Mercurial Mercurial > SEES-hacks / annotate
summary | shortlog | changelog | graph | tags | bookmarks | branches | files | changeset | file | latest | revisions | annotate | diff | comparison | raw | help
Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
web/html/ch2intro.html
author amit@thunder
Fri, 05 Feb 2010 23:42:24 +0530
changeset 1 672eaaab9204
parent 0 8083d21c0020
permissions -rw-r--r--
Added some new html files that failed earlier during change from rst
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     1
 
<html>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     2
 
<head>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     3
 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
     4
 
<title>Intro</title>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     5
 
<link rel="shortcut icon" type="image/png" href="/review/support/figs/favicon.png">
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     6
 
<script type="text/javascript" src="/review/support/jquery-min.js"></script>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     7
 
<script type="text/javascript" src="/review/support/form.js"></script>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     8
 
<script type="text/javascript" src="/review/support/hsbook.js"></script>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
     9
 
<meta name="generator" content="DocBook XSL Stylesheets V1.75.1">
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    10
 
</head>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    11
 
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="chapter" id="ch2intro">
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    12
 
<div class="titlepage"></div>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    13
 
<div class="toc">
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    14
 
<p><b>Table of Contents</b></p>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    15
 
<dl>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    16
 
<dt><span class="article"><a href="#id2931272"></a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    17
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    18
 
<dt><span class="section"><a href="#id2741397">1. Introducing Linux</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    19
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    20
 
<dt><span class="section"><a href="#id2929092">1.1. Historical Background</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    21
 
<dt><span class="section"><a href="#id2982331">1.2. Design and Implications</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    22
 
<dt><span class="section"><a href="#id2982596">1.3. Reasons for Using Linux</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    23
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    24
 
<dt><span class="section"><a href="#id2982723">2. Getting Started</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    25
 
<dd><dl><dt><span class="section"><a href="#id2982731">2.1. Logging in, activating the user interface and logging out</a></span></dt></dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    26
 
<dt><span class="section"><a href="#id2983003">3. Basic Commands</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    27
 
<dd><dl>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    28
 
<dt><span class="section"><a href="#id2983011">3.1. ls</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    29
 
<dt><span class="section"><a href="#id2983169">3.2. date</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    30
 
<dt><span class="section"><a href="#id2983227">3.3. cd</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    31
 
<dt><span class="section"><a href="#id2983324">3.4. who</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    32
 
<dt><span class="section"><a href="#id2983404">3.5. mkdir</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    33
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    34
 
<dt><span class="section"><a href="#id2983578">4. Getting Help</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    35
 
<dd><dl>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    36
 
<dt><span class="section"><a href="#id2983586">4.1. apropos and whatis</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    37
 
<dt><span class="section"><a href="#id2983667">4.2. man</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    38
 
<dt><span class="section"><a href="#id2983870">4.3. info</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    39
 
<dt><span class="section"><a href="#id2983961">4.4. --help</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    40
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    41
 
<dt><span class="section"><a href="#id2984014">5. Basic file handling</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    42
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    43
 
<dt><span class="section"><a href="#id2984023">5.1. cp</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    44
 
<dt><span class="section"><a href="#id2984334">5.2. mv</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    45
 
<dt><span class="section"><a href="#id2984483">5.3. rm</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    46
 
</dl></dd>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    47
 
<dt><span class="section"><a href="#id2984653">6. Command Line Arguments</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    48
 
<dt><span class="section"><a href="#id2984746">7. Basic Text Processing</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    49
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    50
 
<dt><span class="section"><a href="#id2984755">7.1. head</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    51
 
<dt><span class="section"><a href="#id2984842">7.2. tail</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    52
 
<dt><span class="section"><a href="#id2984970">7.3. cut</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    53
 
<dt><span class="section"><a href="#id2985055">7.4. paste</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    54
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    55
 
<dt><span class="section"><a href="#id2985190">8. Shell Meta Characters</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    56
 
<dt><span class="section"><a href="#id2985297">9. Looking At Files</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    57
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    58
 
<dt><span class="section"><a href="#id2985305">9.1. cat</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    59
 
<dt><span class="section"><a href="#id2985493">9.2. more</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    60
 
<dt><span class="section"><a href="#id2985608">9.3. less</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    61
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    62
 
<dt><span class="section"><a href="#id2985848">10. Directory Structure</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    63
 
<dd><dl>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    64
 
<dt><span class="section"><a href="#id2986117">10.1. man hier</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    65
 
<dt><span class="section"><a href="#id2986133">10.2. ls -l</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    66
 
</dl></dd>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    67
 
<dt><span class="section"><a href="#id2986156">11. Permissions and Ownership</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    68
 
<dd><dl><dt><span class="section"><a href="#id2986165">11.1. chmod</a></span></dt></dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    69
 
<dt><span class="section"><a href="#id2986929">12. Redirection and Piping</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    70
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    71
 
<dt><span class="section"><a href="#id2986966">12.1. Redirecting standard input and standard output</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    72
 
<dt><span class="section"><a href="#id2987035">12.2. Piping</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    73
 
<dt><span class="section"><a href="#id2987096">12.3. Redirecting to and from the standard file handles</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    74
 
<dt><span class="section"><a href="#id2987301">12.4. Chained pipelines</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    75
 
<dt><span class="section"><a href="#id2987335">12.5. Redirect to multiple outputs</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    76
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    77
 
<dt><span class="section"><a href="#id2987365">13. More Text Processing</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    78
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    79
 
<dt><span class="section"><a href="#id2987374">13.1. grep</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    80
 
<dt><span class="section"><a href="#id2987563">13.2. tr</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    81
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    82
 
<dt><span class="section"><a href="#id2987713">14. Elementary Regex</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    83
 
<dd><dl><dt><span class="section"><a href="#id2988062">14.1. Lazy quantification</a></span></dt></dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    84
 
<dt><span class="section"><a href="#id2988138">15. One Liners</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    85
 
</dl></dd>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    86
 
</dl>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    87
 
</div>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    88
 
<div class="article">
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    89
 
<div class="titlepage">
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    90
 
<div><div><h2 class="title" id="id2931272"></a></h2></div></div>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    91
 
<hr>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    92
 
</div>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    93
 
<div class="toc">
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    94
 
<p><b>Table of Contents</b></p>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
    95
 
<dl>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    96
 
<dt><span class="section"><a href="#id2741397">1. Introducing Linux</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    97
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    98
 
<dt><span class="section"><a href="#id2929092">1.1. Historical Background</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
    99
 
<dt><span class="section"><a href="#id2982331">1.2. Design and Implications</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   100
 
<dt><span class="section"><a href="#id2982596">1.3. Reasons for Using Linux</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   101
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   102
 
<dt><span class="section"><a href="#id2982723">2. Getting Started</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   103
 
<dd><dl><dt><span class="section"><a href="#id2982731">2.1. Logging in, activating the user interface and logging out</a></span></dt></dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   104
 
<dt><span class="section"><a href="#id2983003">3. Basic Commands</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   105
 
<dd><dl>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   106
 
<dt><span class="section"><a href="#id2983011">3.1. ls</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   107
 
<dt><span class="section"><a href="#id2983169">3.2. date</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   108
 
<dt><span class="section"><a href="#id2983227">3.3. cd</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   109
 
<dt><span class="section"><a href="#id2983324">3.4. who</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   110
 
<dt><span class="section"><a href="#id2983404">3.5. mkdir</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   111
 
</dl></dd>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   112
 
<dt><span class="section"><a href="#id2983578">4. Getting Help</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   113
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   114
 
<dt><span class="section"><a href="#id2983586">4.1. apropos and whatis</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   115
 
<dt><span class="section"><a href="#id2983667">4.2. man</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   116
 
<dt><span class="section"><a href="#id2983870">4.3. info</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   117
 
<dt><span class="section"><a href="#id2983961">4.4. --help</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   118
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   119
 
<dt><span class="section"><a href="#id2984014">5. Basic file handling</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   120
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   121
 
<dt><span class="section"><a href="#id2984023">5.1. cp</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   122
 
<dt><span class="section"><a href="#id2984334">5.2. mv</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   123
 
<dt><span class="section"><a href="#id2984483">5.3. rm</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   124
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   125
 
<dt><span class="section"><a href="#id2984653">6. Command Line Arguments</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   126
 
<dt><span class="section"><a href="#id2984746">7. Basic Text Processing</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   127
 
<dd><dl>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   128
 
<dt><span class="section"><a href="#id2984755">7.1. head</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   129
 
<dt><span class="section"><a href="#id2984842">7.2. tail</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   130
 
<dt><span class="section"><a href="#id2984970">7.3. cut</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   131
 
<dt><span class="section"><a href="#id2985055">7.4. paste</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   132
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   133
 
<dt><span class="section"><a href="#id2985190">8. Shell Meta Characters</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   134
 
<dt><span class="section"><a href="#id2985297">9. Looking At Files</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   135
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   136
 
<dt><span class="section"><a href="#id2985305">9.1. cat</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   137
 
<dt><span class="section"><a href="#id2985493">9.2. more</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   138
 
<dt><span class="section"><a href="#id2985608">9.3. less</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   139
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   140
 
<dt><span class="section"><a href="#id2985848">10. Directory Structure</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   141
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   142
 
<dt><span class="section"><a href="#id2986117">10.1. man hier</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   143
 
<dt><span class="section"><a href="#id2986133">10.2. ls -l</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   144
 
</dl></dd>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   145
 
<dt><span class="section"><a href="#id2986156">11. Permissions and Ownership</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   146
 
<dd><dl><dt><span class="section"><a href="#id2986165">11.1. chmod</a></span></dt></dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   147
 
<dt><span class="section"><a href="#id2986929">12. Redirection and Piping</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   148
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   149
 
<dt><span class="section"><a href="#id2986966">12.1. Redirecting standard input and standard output</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   150
 
<dt><span class="section"><a href="#id2987035">12.2. Piping</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   151
 
<dt><span class="section"><a href="#id2987096">12.3. Redirecting to and from the standard file handles</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   152
 
<dt><span class="section"><a href="#id2987301">12.4. Chained pipelines</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   153
 
<dt><span class="section"><a href="#id2987335">12.5. Redirect to multiple outputs</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   154
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   155
 
<dt><span class="section"><a href="#id2987365">13. More Text Processing</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   156
 
<dd><dl>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   157
 
<dt><span class="section"><a href="#id2987374">13.1. grep</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   158
 
<dt><span class="section"><a href="#id2987563">13.2. tr</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   159
 
</dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   160
 
<dt><span class="section"><a href="#id2987713">14. Elementary Regex</a></span></dt>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   161
 
<dd><dl><dt><span class="section"><a href="#id2988062">14.1. Lazy quantification</a></span></dt></dl></dd>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   162
 
<dt><span class="section"><a href="#id2988138">15. One Liners</a></span></dt>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   163
 
</dl>
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   164
 
</div>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   165
 
<div class="section" title="1. Introducing Linux">
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   166
 
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   167
 
<a name="id2741397"></a>1. Introducing Linux</h2></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   168
 
<p id="ch2intro_1"></a>(Attribution : A significant chunk of the content under this section is based on data from Wikipedia and the Linux Documentation Project)</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   169
 
<p id="ch2intro_2"></a>Linux (usually pronounced ˈlɪnəks') is a generic term referring to Unix-like computer operating systems based on the Linux kernel, where a kernel is the intermediate layer between the hardware and the applications. The kernel is, on an abstract level, the core of (most) operating systems, that manages the various system resources. The development of the Linux OS is considered the basis for Free and Open Source Software (FOSS) collaboration since typically the underlying source code can be used, modified freely, and redistributed by anyone under the terms of the GNU (a recursive acronym for "GNU's Not Unix!") Global Public License (GPL) and other free software licences. This freedom to access and reuse various components of a system, is one of the primary reasons for the popularity of Linux.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   170
 
<p id="ch2intro_3"></a>Linux is installed on a variety of computer hardware, that include mobile phones, embedded devices and supercomputers, but is infamous for its use in servers.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   171
 
<p id="ch2intro_4"></a>The name "Linux"  comes from the Linux kernel, originally written in 1991 by Linus Torvalds. The rest of the system usually comprises components such as the Apache HTTP Server, the X Window System, the GNOME and KDE desktop environments, and utilities and libraries from the GNU Project (announced in 1983 by Richard Stallman). Commonly-used applications with desktop Linux systems include the Mozilla Firefox web-browser and the OpenOffice.org office application suite. The GNU contribution is the basis for the Free Software Foundation's preferred name GNU/Linux. The kernel's mascot is a penguin named "Tux". Mozilla Firefox and OpenOffice.org are open-source projects which can be run on most Operating Systems, including proprietary ones.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   172
 
<div class="section" title="1.1. Historical Background">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   173
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   174
 
<a name="id2929092"></a>1.1. Historical Background</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   175
 
<div class="section" title="1.1.1. Events leading to the creation">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   176
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   177
 
<a name="id2928965"></a>1.1.1. Events leading to the creation</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   178
 
<div class="itemizedlist"><ul class="itemizedlist" type="*">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   179
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_5"></a>The Unix operating system was developed in the 1960s and released for public use in 1970. Its accessibility and portability caused it to be widely adopted, copied and modified by academic institutions and businesses. Its design became influential to authors of other systems. Other free operating systems include the Berkeley Software Distribution (BSD), developed at the University of California at Berkeley, and MINIX which was released by Andrew S. Tanenbaum. The development and adoption of BSD and MINIX were limited due to various reasons, and this lack of a widely-adopted and free kernel triggered Linus Torvalds into starting his project.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   180
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_6"></a>In 1983, Richard Stallman started the GNU project with the goal of creating a free UNIX-like operating system. As part of this work, he wrote the GNU General Public License (GPL). By the early 1990s there was almost enough available software to create a full operating system. However, the GNU kernel, called Hurd, failed to attract enough attention from developers leaving GNU incomplete.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   181
 
</ul></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   182
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   183
 
<div class="section" title="1.1.2. The Creation of Linux">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   184
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   185
 
<a name="id2982286"></a>1.1.2. The Creation of Linux</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   186
 
<p id="ch2intro_7"></a>In 1991, Linus Torvalds began a project at the University of Helsinki that later became the Linux kernel. It was initially a terminal (command-line) emulator, which Torvalds used to access the large UNIX servers of the university. He wrote the program targeting just the hardware he was using and independent of an operating system because he wanted to use the functions of his computer with an 80386 processor. Development was done on Minix using the GNU C compiler. This application is still the main choice for compiling Linux today (although the code can be built with other compilers, such as the Intel C Compiler).</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   187
 
<p id="ch2intro_8"></a>Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components, which constitute a vast body of work and including kernel modules, and user applications and libraries. Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   188
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   189
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   190
 
<div class="section" title="1.2. Design and Implications">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   191
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   192
 
<a name="id2982331"></a>1.2. Design and Implications</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   193
 
<p id="ch2intro_9"></a>A Linux-based system is a modular Unix-like operating system, deriving much of its basic design from principles established in Unix earlier. Such a system uses a monolithic kernel, called the Linux kernel, which handles process control, networking, and peripheral and file system access. Device drivers are integrated directly with the kernel. Separate projects that interface with the kernel provide much of the system's higher-level functionality. The GNU userland is an important part of most Linux-based systems, providing the most common implementation of the C library, a popular shell, and many of the common Unix tools which carry out many basic operating system tasks. The graphical user interface (or GUI) used by most Linux systems is based on the "X Window System".</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   194
 
<div class="section" title="1.2.1. User Interface">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   195
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   196
 
<a name="id2982356"></a>1.2.1. User Interface</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   197
 
<p id="ch2intro_a"></a>Users can control a Linux-based system through a command line interface (or CLI), a graphical user interface (or GUI), or through controls attached to the associated hardware (this is common for embedded systems). For desktop systems, the default mode is usually the GUI. On desktop machines, "KDE", "GNOME" and "Xfce" are the most popular user interfaces,though a variety of additional user interfaces exist. Most popular user interfaces run on top of the "X Window System" (or X), which enables a graphical application running on one machine to be displayed and controlled from another in a network.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   198
 
<p id="ch2intro_b"></a>A Linux system also provides a CLI of some sort through a shell, which is the traditional way of interacting with a Unix system. A Linux distribution specialized for servers may use the CLI as its only interface. A “headless system” (system run without even a monitor) can be controlled by the command line via a remote-control protocol such as SSH or telnet. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication. A graphical terminal emulator program is often used to access the CLI from a Linux desktop.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   199
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   200
 
<div class="section" title="1.2.2. Development">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   201
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   202
 
<a name="id2982408"></a>1.2.2. Development</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   203
 
<p id="ch2intro_c"></a>The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open source software. Linux is not the only such operating system, although it is by far the most widely used. Some free and open source software licenses are based on the principle of "copyleft", a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU GPL, is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU project.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   204
 
<p id="ch2intro_d"></a>Linux based distributions are intended by developers for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX, SUS, ISO and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.Free software projects, although developed in a collaborative fashion, are often produced independently of each other. The fact that the software licenses explicitly permit redistribution, however, provides a basis for larger scale projects that collect the software produced by stand-alone projects and make it available all at once in the form of a Linux distribution.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   205
 
<p id="ch2intro_e"></a>A Linux distribution, commonly called a "distro", is a project that manages a remote collection of system software and application software packages available for download and installation through a network connection. This allows the user to adapt the operating system to his/her specific needs. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. A distribution can be installed using a CD that contains distribution-specific software for initial system installation and configuration. A package manager such as Synaptic or YAST allows later package upgrades and installations. A distribution is responsible for the default configuration of the installed Linux kernel, general system security, and more generally integration of the different software packages into a coherent whole.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   206
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   207
 
<div class="section" title="1.2.3. Community">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   208
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   209
 
<a name="id2982463"></a>1.2.3. Community</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   210
 
<p id="ch2intro_f"></a>A distribution is largely driven by its developer and user communities. Some vendors develop and fund their distributions on a volunteer basis. Examples include Debian and the Debian-based, Ubuntu. Others maintain a community version of their commercial distributions, as Red Hat does with Fedora.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   211
 
<p id="ch2intro_10"></a>In many cities and regions, local associations known as Linux Users Groups (LUGs) seek to promote their preferred distribution and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. Many Internet communities also provide support to Linux users and developers. Most distributions and free software / open source projects have IRC (Internet Relay Chat) chatrooms or newsgroups. Online forums are another means for support. Linux distributions host mailing lists; commonly there will be a specific topic such as usage or development for a given list. All these can be found simply by running an appropriate search on Google.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   212
 
<p id="ch2intro_11"></a>Although Linux distributions are generally available without charge, several large corporations sell, support, and contribute to the development of the components of the system and of free software. These include Dell, IBM, HP, Oracle, Sun Microsystems, Novell, Nokia. A number of corporations, notably Red Hat, have built their entire business around Linux distributions.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   213
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   214
 
<div class="section" title="1.2.4. Can I make a profit out of running a business involving Linux?">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   215
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   216
 
<a name="id2982506"></a>1.2.4. Can I make a profit out of running a business involving Linux?</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   217
 
<p id="ch2intro_12"></a>The answer is, "Yes!". The free software licenses, on which the various software packages of a distribution built on the Linux kernel are based, explicitly accommodate and encourage commercialization; the relationship between a Linux distribution as a whole and individual vendors may be seen as symbiotic. One common business model of commercial suppliers is charging for support, especially for business users. A number of companies also offer a specialized business version of their distribution, which adds proprietary support packages and tools to administer higher numbers of installations or to simplify administrative tasks. Another business model is to give away the software in order to sell hardware. Examples of corporations that are extensively (and sometimes exclusively) open-source and Linux-powered , with successful revenue generation models involving these, are Google, SUN, Mozilla, etc.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   218
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   219
 
<div class="section" title="1.2.5. Programming on Linux">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   220
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   221
 
<a name="id2982552"></a>1.2.5. Programming on Linux</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   222
 
<p id="ch2intro_13"></a>Most Linux distributions support dozens of programming languages. The most common collection of utilities for building both Linux applications and operating system programs is found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system. Amongst others, GCC provides compilers for Ada, C, C++, Java, and Fortran. The Linux kernel itself is written to be compiled with GCC. Proprietary compilers for Linux include the Intel C++ Compiler, Sun Studio, and IBM XL C/C++ Compiler.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   223
 
<p id="ch2intro_14"></a>Most distributions also include support for PHP, Perl, Ruby, Python and other dynamic languages. Examples of languages that are less common, but still supported, are C# via the Mono project, sponsored by Novell, and Scheme. A number of Java Virtual Machines and development kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM's J2SE RE, as well as many open-source projects like Kaffe.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   224
 
<p id="ch2intro_15"></a>The two main frameworks for developing graphical applications are those of GNOME and KDE. These projects are based on the GTK+ and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of Integrated Development Environments (IDEs) available including Anjuta, Code::Blocks, Eclipse, KDevelop, Lazarus, MonoDevelop, NetBeans, and Omnis Studio while the long-established editors Vim and Emacs remain popular.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   225
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   226
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   227
 
<div class="section" title="1.3. Reasons for Using Linux">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   228
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   229
 
<a name="id2982596"></a>1.3. Reasons for Using Linux</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   230
 
<div class="itemizedlist"><ul class="itemizedlist" type="*"><li class="listitem" style="list-style-type: *"><p id="ch2intro_16"></a>Linux is free:</p></li></ul></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   231
 
<p id="ch2intro_17"></a>As in "free beer". Linux can be downloaded in its entirety from the Internet completely for free. No registration fees, no costs per user, free updates, and freely available source code in case you want to change the behavior of your system.
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   232
 
Most of all, Linux is free as in "free speech":
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   233
 
The license commonly used is the GNU Public License (GPL). The license says that anybody who may want to do so, has the right to change Linux and eventually to redistribute a changed version, on the one condition that the code is still available after redistribution. In practice, you are free to grab a kernel image and sell the new code, as long as your customers can still have a copy of that code.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   234
 
<div class="itemizedlist"><ul class="itemizedlist" type="*"><li class="listitem" style="list-style-type: *"><p id="ch2intro_18"></a>Linux is portable to any hardware platform:</p></li></ul></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   235
 
<p id="ch2intro_19"></a>A vendor, who wants to sell a new type of computer and who does not know what kind of OS his/her new machine will run, can take a Linux kernel and make it work on his/her hardware, because documentation related to this activity is freely available.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   236
 
<div class="itemizedlist"><ul class="itemizedlist" type="*"><li class="listitem" style="list-style-type: *"><p id="ch2intro_1a"></a>Linux was made to keep on running:</p></li></ul></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   237
 
<p id="ch2intro_1b"></a>As with UNIX, a Linux system expects to run without rebooting all the time. That is why a lot of tasks are being executed at night or scheduled automatically for other times, resulting in higher availability during busier periods and a more balanced use of the hardware. This property allows for Linux to be applicable to environments where people do not have the time or the possibility to control their systems constantly.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   238
 
<div class="itemizedlist"><ul class="itemizedlist" type="*"><li class="listitem" style="list-style-type: *"><p id="ch2intro_1c"></a>Linux is secure and versatile:</p></li></ul></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   239
 
<p id="ch2intro_1d"></a>The security model used in Linux is based on the UNIX idea of security, which is known to be robust and of proven quality. But Linux is not only safe from attacks from the Internet: it will adapt equally to other situations, utilizing the same high standards for security.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   240
 
<div class="itemizedlist"><ul class="itemizedlist" type="*"><li class="listitem" style="list-style-type: *"><p id="ch2intro_1e"></a>Linux is scalable:</p></li></ul></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   241
 
<p id="ch2intro_1f"></a>From a Palmtop with 2 MB of memory to a petabyte storage cluster with hundreds of nodes: add or remove the appropriate packages and Linux fits all. One does not need a supercomputer anymore,because you can use Linux to do big things using the building blocks provided with the system. If one wants to do little things, such as making an operating system for an embedded processor or just recycling your old 486, Linux will do that as well.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   242
 
<div class="itemizedlist"><ul class="itemizedlist" type="*"><li class="listitem" style="list-style-type: *"><p id="ch2intro_20"></a>The Linux OS and Linux applications have very short debug−times:</p></li></ul></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   243
 
<p id="ch2intro_21"></a>Because Linux has been developed and tested by thousands of people, both errors and people to fix them are found very quickly. It often happens that there are only a couple of hours between discovery and fixing of a bug.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   244
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   245
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   246
 
<div class="section" title="2. Getting Started">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   247
 
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   248
 
<a name="id2982723"></a>2. Getting Started</h2></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   249
 
<div class="section" title="2.1. Logging in, activating the user interface and logging out">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   250
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   251
 
<a name="id2982731"></a>2.1. Logging in, activating the user interface and logging out</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   252
 
<p id="ch2intro_22"></a>In order to work on a Linux system directly, one needs to provide a user name and password. You always need to authenticate to the system. Most PC−based Linux systems have two basic modes for a system to run in: either quick and clean in text console mode,which includes with mouse, multitasking and multi−user features, or in graphical console mode, which looks better but eats more system resources.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   253
 
<div class="section" title="2.1.1. Graphical Mode">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   254
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   255
 
<a name="id2982761"></a>2.1.1. Graphical Mode</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   256
 
<p id="ch2intro_23"></a>This is the default nowadays on most desktop computers. You know you will be connecting to the system using graphical mode when you are first asked for your user name, and then to type your password.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   257
 
<p id="ch2intro_24"></a>To log in, make sure the mouse pointer is in the login window, provide your user name and password to the system and click <span class="emphasis"><em>OK</em></span> or press <span class="emphasis"><em>Enter</em></span>.
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   258
 
It is generally considered a bad idea to connect (graphically) using the root user name, the system adminstrator's account, since the use of graphics includes running a lot of extra programs, in root's case with a lot of extra permissions. To keep all risks as low as possible, use a normal user account to connect graphically. But there are enough risks to keep this in mind as a general advice, for all use of the root account: only log in as root when extra privileges are required.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   259
 
<p id="ch2intro_25"></a>After entering your user name/password combination, it can take a little while before the graphical environment is started, depending on the CPU speed of your computer, on the software you use and on your personal settings.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   260
 
<p id="ch2intro_26"></a>To continue, you will need to open a <span class="emphasis"><em>terminal window</em></span> or <span class="emphasis"><em>xterm</em></span> for short (X being the name for the underlying software supporting the graphical environment). This program can be found in the <span class="emphasis"><em>Applications−&gt;Utilities-&gt;System Tools</em></span> or <span class="emphasis"><em>Internet menu</em></span>, depending on what window manager you are using. There might be icons that you can use as a shortcut to get an <span class="emphasis"><em>xterm</em></span> window as well, and clicking the right mouse button on the desktop background will usually present you with a menu containing a terminal window application.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   261
 
<p id="ch2intro_27"></a>While browsing the menus, you will notice that a lot of things can be done without entering commands via the keyboard. For most users, the good old point−n−click method of dealing with the computer will do. But for those who want to enter the "heart" of the system, a tool stronger than a mouse will be required to handle the various tasks. This tool is the shell, and when in graphical mode, we activate our shell by opening a terminal window.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   262
 
<p id="ch2intro_28"></a>A terminal window should always show a command prompt when you open one. This terminal shows a standard prompt, which displays the user's login name, and the current working directory, represented by the twiddle (~)</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   263
 
<p id="ch2intro_29"></a>Another common form for a prompt is this one:
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   264
 
[</p>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   265
 
<div class="reference">
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   266
 
<div class="titlepage"><hr></div>user@host</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   267
 
<p> dir]</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   268
 
<p id="ch2intro_2a"></a>In the above example, <span class="emphasis"><em>user</em></span> will be your login name, <span class="emphasis"><em>hosts</em></span> the name of the machine you are working on, and <span class="emphasis"><em>dir</em></span> an indication of your current location in the file system. Prompts can display all kinds of information, but they are not part of the commands you are giving to your system. To disconnect from the system in graphical mode, you need to close all terminal windows and other applications. After that, hit the <span class="emphasis"><em>logout</em></span> icon or find <span class="emphasis"><em>Log Out</em></span> in the menu. Closing everything is not really necessary, and the system can do this for you, but session management might put all currently open applications back on your screen when you connect again, which takes longer and is not always the desired effect. However, this behavior is configurable.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   269
 
<p id="ch2intro_2b"></a>When you see the login screen again, asking to enter user name and password, logout was successful.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   270
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   271
 
<div class="section" title="2.1.2. Text Mode">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   272
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   273
 
<a name="id2982916"></a>2.1.2. Text Mode</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   274
 
<p id="ch2intro_2c"></a>One is in text mode when the whole screen is black, showing (in most cases white) characters. A text mode login screen typically shows some information about the machine you are working on, the name of the machine and a prompt waiting for you to log in.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   275
 
<p id="ch2intro_2d"></a>The login is different from a graphical login, in that you have to hit the <span class="emphasis"><em>Enter</em></span> key after providing your user name, because there are no buttons on the screen that you can click with the mouse. Then you should type your password, followed by another <span class="emphasis"><em>Enter</em></span>. You will not see any indication that you are entering something, not even an asterisk, and you won't see the cursor move. But this is normal on Linux and is done for security
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   276
 
reasons.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   277
 
<p id="ch2intro_2e"></a>When the system has accepted you as a valid user, you may get some more information, called the <span class="emphasis"><em>message of the day</em></span>, which can be anything. Additionally, it is popular on UNIX systems to display a fortune cookie, which contains some general wise or unwise (this is up to you) thoughts. After that, you will be given a shell, indicated with the same prompt that you would get in graphical mode.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   278
 
<p id="ch2intro_2f"></a>Also in text mode: log in as root only to do setup and configuration that absolutely requires administrator privileges, such as adding users, installing software packages, and performing network and other system configuration. Once you are finished, immediately leave the special account and resume your work as a non−privileged user.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   279
 
<p id="ch2intro_30"></a>Logging out is done by entering the <span class="emphasis"><em>logout</em></span> command, followed by Enter. You are successfully disconnected from the system when you see the login screen again.Don't power−off the computer after logging out. It is not meant to be shut off without application of the proper procedures for halting the system. Powering it off without going through the halting process might cause severe damage!</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   280
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   281
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   282
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   283
 
<div class="section" title="3. Basic Commands">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   284
 
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   285
 
<a name="id2983003"></a>3. Basic Commands</h2></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   286
 
<div class="section" title="3.1. ls">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   287
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   288
 
<a name="id2983011"></a>3.1. ls</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   289
 
<p id="ch2intro_31"></a>When invoked without any arguments, <span class="emphasis"><em>ls</em></span> lists the files in the current working directory. A directory that is not the current working directory can be specified and ls will list the files there. The user also may specify any list of files and directories. In this case, all files and all contents of specified directories will be listed. The name <span class="emphasis"><em>ls</em></span> is derived from <span class="emphasis"><em>list segments</em></span> which was used in earlier systems.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   290
 
<p id="ch2intro_32"></a>Files whose names start with "." are not listed, unless the <span class="emphasis"><em>-a</em></span> flag is specified or the files are specified explicitly.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   291
 
<p id="ch2intro_33"></a>Without options, <span class="emphasis"><em>ls</em></span> displays files in a bare format. This bare format however makes it difficult to establish the type, permissions, and size of the files. The most common options to reveal this information or change the list of files are:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   292
 
<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   293
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_34"></a><span class="emphasis"><em>-l</em></span> long format, displaying Unix file types, permissions, number of hard links, owner, group, size, date, and filename</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   294
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_35"></a><span class="emphasis"><em>-F</em></span> appends a character revealing the nature of a file, for example, * for an executable, or / for a directory. Regular files have no suffix.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   295
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_36"></a><span class="emphasis"><em>-a</em></span> lists all files in the given directory, including those whose names start with "." (which are hidden files in Unix). By default, these files are excluded from the list.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   296
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_37"></a><span class="emphasis"><em>-R</em></span> recursively lists subdirectories. The command ls -R / would therefore list all files.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   297
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_38"></a><span class="emphasis"><em>-d</em></span> shows information about a symbolic link or directory, rather than about the link's target or listing the contents of a directory.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   298
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_39"></a><span class="emphasis"><em>-t</em></span> sort the list of files by modification time.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   299
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_3a"></a><span class="emphasis"><em>-h</em></span> print sizes in human readable format. (e.g., 1K, 234M, 2G, etc.)</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   300
 
</ul></div>&lt;/block_quote&gt;</span><p id="ch2intro_3b"></a>In some environments, providing the option <span class="emphasis"><em>--color</em></span> (for GNU ls) or <span class="emphasis"><em>-G</em></span> (FreeBSD ls) causes ls to highlight different types of files with different colors, instead of with characters as <span class="emphasis"><em>-F</em></span> would. To determine what color to use for a file, GNU <span class="emphasis"><em>ls</em></span> checks the Unix file type, the file permissions, and the file extension, while FreeBSD <span class="emphasis"><em>ls</em></span> checks only the Unix file type and file permissions.:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   301
 
<pre class="programlisting">$ ls
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   302
 
jeeves.rst psmith.html blandings.html
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   303
 
$ ls -l
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   304
 
drwxr--r--   1 plum  editors   4096  jeeves
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   305
 
-rw-r--r--   1 plum  editors  30405  psmith
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   306
 
-r-xr-xr-x   1 plum  plum      8460  blandings</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   307
 
<p id="ch2intro_3c"></a>Here "$" actually is the beginning of the prompt. This is typical in most Unix-based systems.</p>
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   308
 
</div>
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   309
 
<div class="section" title="3.2. date">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   310
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   311
 
<a name="id2983169"></a>3.2. date</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   312
 
<p id="ch2intro_3d"></a>The Unix date command displays the time and date. The super-user can use it to set the system clock.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   313
 
<p id="ch2intro_3e"></a>With no options, the date command displays the current date and time, including the abbreviated day name, abbreviated month name, day of the month, the time separated by colons, the timezone name, and the year. For example:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   314
 
<pre class="programlisting">$date
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   315
 
Tue Sep  8 12:01:45 IST 2009</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   316
 
<p id="ch2intro_3f"></a>On some systems to set the current date and time to September 8, 2004 01:22 you type:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   317
 
<pre class="programlisting">$date --set="20040908 01:22"</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   318
 
<p id="ch2intro_40"></a>In order to view the various options for the <span class="emphasis"><em>date</em></span> command, type:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   319
 
<pre class="programlisting">$man date</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   320
 
<p id="ch2intro_41"></a>This will take you to the "Manual" page comprising of all the details on the <span class="emphasis"><em>date</em></span> command. You can return to the terminal from the "man" page by pressing the <span class="emphasis"><em>Esc</em></span> key in the keyboard and typing ":q" in that order.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   321
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   322
 
<div class="section" title="3.3. cd">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   323
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   324
 
<a name="id2983227"></a>3.3. cd</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   325
 
<p id="ch2intro_42"></a>This stands for "change directory". When one wants to go up to the parent directory, bypassing the tree of directories one has entered, “ cd ..” can be used.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   326
 
<p id="ch2intro_43"></a>One dot '.' represents the current directory while two dots '..' represent the parent directory.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   327
 
<p id="ch2intro_44"></a>“ cd -” will return you to the previous directory (a bit like an “undo”).</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   328
 
<p id="ch2intro_45"></a>You can also use cd absolute path or cd relative path (see below):</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   329
 
<p id="ch2intro_46"></a>Absolute paths:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   330
 
<span style="color: red">&lt;block_quote&gt;<p id="ch2intro_47"></a>An “ absolute path” is easily recognised from the leading forward slash, /. The / means that you start at the top level directory and continue down.</p>&lt;/block_quote&gt;</span><p id="ch2intro_48"></a>For example to get to /boot/grub you would type:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   331
 
<pre class="programlisting">$cd /boot/grub</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   332
 
<p id="ch2intro_49"></a>This is an absolute path because you start at the top of the hierarchy and go downwards from there (it doesn't matter where in the filesystem you were when you typed the command).</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   333
 
<p id="ch2intro_4a"></a>Relative paths:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   334
 
<span style="color: red">&lt;block_quote&gt;<p id="ch2intro_4b"></a>A “ relative path” doesn't have a preceding slash. Use a relative path when you start from a directory below the top level directory structure. This is dependent on where you are in the filesystem.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   335
 
<p id="ch2intro_4c"></a>For example if you are in root's home directory and want to get to /root/music, you type:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   336
 
<pre class="programlisting">$ cd music</pre>&lt;/block_quote&gt;</span><p id="ch2intro_4d"></a>Please note that there is no / using the above cd command. Using a / would cause this to be an absolute path, working from the top of the hierarchy downward.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   337
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   338
 
<div class="section" title="3.4. who">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   339
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   340
 
<a name="id2983324"></a>3.4. who</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   341
 
<p id="ch2intro_4e"></a>The standard Unix command <span class="emphasis"><em>who</em></span> displays a list of users who are currently logged into a computer.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   342
 
<p id="ch2intro_4f"></a>The <span class="emphasis"><em>who</em></span> command is related to the command <span class="emphasis"><em>w</em></span>, which provides the same information but also displays additional data and statistics.:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   343
 
<pre class="programlisting">$who
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   344
 
beeblebrox tty7         2009-09-08 10:50 (:0)
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   345
 
beeblebrox pts/0        2009-09-08 11:25 (:0.0)
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   346
 
dumbledore pts/1        2009-09-08 18:11 (potter.xyz.in)
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   347
 
beeblebrox pts/2        2009-09-08 18:53 (:0.0)</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   348
 
<p id="ch2intro_50"></a>The command can be invoked with the arguments <span class="emphasis"><em>am i</em></span> or <span class="emphasis"><em>am I</em></span> (so it is invoked as <span class="emphasis"><em>who am i</em></span> or * who am I*), showing information about the current terminal only (see the <span class="emphasis"><em>-m</em></span> option below, of which this invocation is equivalent).</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   349
 
<p id="ch2intro_51"></a>In order to find out the various options that can be appended to the <span class="emphasis"><em>who</em></span> command, check the <span class="emphasis"><em>man</em></span> page by typing out the following in the terminal:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   350
 
<pre class="programlisting">$man who</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   351
 
<p id="ch2intro_52"></a>This will take you to the "Manual" page containing details about the <span class="emphasis"><em>who</em></span> command</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   352
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   353
 
<div class="section" title="3.5. mkdir">
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   354
 
<div class="titlepage"><div><div><h3 class="title">
1
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   355
 
<a name="id2983404"></a>3.5. mkdir</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   356
 
<p id="ch2intro_53"></a>This command is used to make a new directory. Normal usage is as straightforward as follows:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   357
 
<pre class="programlisting">$mkdir name_of_directory</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   358
 
<p id="ch2intro_54"></a>Where <span class="emphasis"><em>name_of_directory</em></span> is the name of the directory one wants to create. When typed as above (ie. normal usage), the new directory would be created within the current directory. On Unix, multiple directories can be specified, and <span class="emphasis"><em>mkdir</em></span> will try to create all of them.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   359
 
<div class="section" title="3.5.1. Options">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   360
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   361
 
<a name="id2983435"></a>3.5.1. Options</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   362
 
<p id="ch2intro_55"></a>On Unix-like operating systems, <span class="emphasis"><em>mkdir</em></span> takes options. Three of the most common options are:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   363
 
<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   364
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_56"></a><span class="emphasis"><em>-p</em></span>: will also create all directories leading up to the given directory that do not exist already. If the given directory already exists, ignore the error.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   365
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_57"></a><span class="emphasis"><em>-v</em></span>: display each directory that mkdir creates. Most often used with -p.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   366
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_58"></a><span class="emphasis"><em>-m</em></span>: specify the octal permissions of directories created by mkdir.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   367
 
</ul></div>&lt;/block_quote&gt;</span><p id="ch2intro_59"></a><span class="emphasis"><em>-p</em></span> is most often used when using mkdir to build up complex directory hierarchies, in case a necessary directory is missing or already there. -m is commonly used to lock down temporary directories used by shell scripts.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   368
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   369
 
<div class="section" title="3.5.2. Examples">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   370
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   371
 
<a name="id2983494"></a>3.5.2. Examples</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   372
 
<p id="ch2intro_5a"></a>An example of <span class="emphasis"><em>-p</em></span> in action is:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   373
 
<pre class="programlisting">$mkdir -p /tmp/a/b/c</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   374
 
<p id="ch2intro_5b"></a>If <span class="emphasis"><em>/tmp/a</em></span> exists but <span class="emphasis"><em>/tmp/a/b</em></span> does not, mkdir will create <span class="emphasis"><em>/tmp/a/b</em></span> before creating <span class="emphasis"><em>/tmp/a/b/c</em></span>.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   375
 
<p id="ch2intro_5c"></a>And an even more powerful command, creating a full tree at once (this however is a Shell extension, nothing mkdir does itself):</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   376
 
<pre class="programlisting">$mkdir -p tmpdir/{trunk/sources/{includes,docs},branches,tags}</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   377
 
<p id="ch2intro_5d"></a>This will create:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   378
 
<span style="color: red">&lt;definition_list&gt;<span style="color: red">&lt;definition_list_item&gt;<span style="color: red">&lt;term&gt;tmpdir  - branches&lt;/term&gt;</span><span style="color: red">&lt;definition&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   379
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_5e"></a>tag</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   380
 
<li class="listitem" style="list-style-type: *"><span style="color: red">&lt;definition_list&gt;<span style="color: red">&lt;definition_list_item&gt;<span style="color: red">&lt;term&gt;trunk - sources - includes&lt;/term&gt;</span><span style="color: red">&lt;definition&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*"><li class="listitem" style="list-style-type: *"><p id="ch2intro_5f"></a>docs</p></li></ul></div>&lt;/definition&gt;</span>&lt;/definition_list_item&gt;</span>&lt;/definition_list&gt;</span></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   381
 
</ul></div>&lt;/definition&gt;</span>&lt;/definition_list_item&gt;</span>&lt;/definition_list&gt;</span>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   382
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   383
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   384
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   385
 
<div class="section" title="4. Getting Help">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   386
 
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   387
 
<a name="id2983578"></a>4. Getting Help</h2></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   388
 
<div class="section" title="4.1. apropos and whatis">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   389
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   390
 
<a name="id2983586"></a>4.1. apropos and whatis</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   391
 
<p id="ch2intro_60"></a>This is a command to search the manual pages files in Unix and Unix-like operating systems.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   392
 
<pre class="programlisting">$ apropos grep
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   393
 
egrep       egrep (1)       Search a file for a pattern using full regular expressions
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   394
 
fgrep       fgrep (1)       Search a file for a fixed-character string
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   395
 
fmlgrep     fmlgrep (1)     Search a file for a pattern
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   396
 
grep        grep (1)        Search a file for a pattern
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   397
 
gzgrep      gzgrep (1)      Search a possibly compressed file for a regular expression
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   398
 
nisgrep     nismatch (1)    Utilities for searching NIS+ tables
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   399
 
pgrep       pgrep (1)       Find or signal a process by name or other attribute
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   400
 
zgrep       zgrep (1)       Search a possibly compressed file for a regular expression
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   401
 
...</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   402
 
<p id="ch2intro_61"></a>In this example, the user uses <span class="emphasis"><em>apropos</em></span> to search for the string "grep", and apropos returns the indicated <span class="emphasis"><em>man</em></span> pages that include the term "grep".</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   403
 
<p id="ch2intro_62"></a>A short index of explanations for commands is available using the <span class="emphasis"><em>whatis</em></span> command, like in the examples below:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   404
 
<pre class="programlisting">$whatis ls
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   405
 
ls (1)           - list directory contents</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   406
 
<p id="ch2intro_63"></a>This displays short information about a command, and the first section in the collection of man pages that contains an appropriate page.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   407
 
<p id="ch2intro_64"></a>If you don't know where to get started and which man page to read, <span class="emphasis"><em>apropos</em></span> gives more information. Say that you do not know how to start a browser, then you could enter the following command:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   408
 
<pre class="programlisting">$apropos browser
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   409
 
gmusicbrowser (1)    - Jukebox for large collections of audio files
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   410
 
infobrowser (1)      - read Info documents
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   411
 
libsmbclient (7)     - An extension library for browsers and that               can be used...
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   412
 
opera (1)            - a standards-compliant graphical Web browser
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   413
 
sensible-browser (1) - sensible editing, paging, and web browsing
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   414
 
smbtree (1)          - A text based smb network browser
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   415
 
tvtk_doc (1)         - A GUI based TVTK documentation search browser.
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   416
 
viewres (1)          - graphical class browser for Xt
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   417
 
w3m (1)              - a text based Web browser and pager
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   418
 
www-browser (1)      - a text based Web browser and pager
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   419
 
...</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   420
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   421
 
<div class="section" title="4.2. man">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   422
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   423
 
<a name="id2983667"></a>4.2. man</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   424
 
<p id="ch2intro_65"></a>Man pages (short for "manual pages") are the extensive documentation that comes preinstalled with almost all substantial Unix and Unix-like operating systems. The Unix command used to display them is <span class="emphasis"><em>man</em></span>. Each page is a self-contained document.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   425
 
<p id="ch2intro_66"></a>To read a manual page for a Unix command, one can use:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   426
 
<pre class="programlisting">$ man &lt;command_name&gt;</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   427
 
<p id="ch2intro_67"></a>at a shell prompt; for example, "man ftp". In order to simplify navigation through the output, <span class="emphasis"><em>man</em></span> generally uses the less terminal pager.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   428
 
<p id="ch2intro_68"></a>Pages are traditionally referred to using the notation "name(section)"; for example, ftp(1). The same page name may appear in more than one section of the manual, this can occur when the names of system calls, user commands, or macro packages coincide. Two examples are <span class="emphasis"><em>man(1)</em></span> and <span class="emphasis"><em>man(7)</em></span>, or <span class="emphasis"><em>exit(2)</em></span> and <span class="emphasis"><em>exit(3)</em></span>. The syntax for accessing the non-default manual section varies between different man implementations. On Linux and <span class="emphasis"><em>BSD, for example, the syntax for reading *printf(3)</em></span> is:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   429
 
<pre class="programlisting">$man 3 printf</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   430
 
<p id="ch2intro_69"></a>Another example:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   431
 
<pre class="programlisting">$man man</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   432
 
<p id="ch2intro_6a"></a>The previous example will take you to the "Manual" page entry about manual pages!</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   433
 
<div class="section" title="4.2.1. Layout">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   434
 
<div class="titlepage"><div><div><h4 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   435
 
<a name="id2983747"></a>4.2.1. Layout</h4></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   436
 
<p id="ch2intro_6b"></a>All man pages follow a common layout that is optimized for presentation on a simple ASCII text display, possibly without any form of highlighting or font control. Sections present may include:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   437
 
<span style="color: red">&lt;definition_list&gt;<span style="color: red">&lt;definition_list_item&gt;<span style="color: red">&lt;term&gt;NAME&lt;/term&gt;</span><span style="color: red">&lt;definition&gt;<p id="ch2intro_6c"></a>The name of the command or function, followed by a one-line description of what it does.</p>&lt;/definition&gt;</span>&lt;/definition_list_item&gt;</span><span style="color: red">&lt;definition_list_item&gt;<span style="color: red">&lt;term&gt;SYNOPSIS&lt;/term&gt;</span><span style="color: red">&lt;definition&gt;<p id="ch2intro_6d"></a>In the case of a command, you get a formal description of how to run it and what command line options it takes. For program functions, a list of the parameters the function takes and which header file contains its definition. For experienced users, this may be all the documentation they need.</p>&lt;/definition&gt;</span>&lt;/definition_list_item&gt;</span><span style="color: red">&lt;definition_list_item&gt;<span style="color: red">&lt;term&gt;DESCRIPTION&lt;/term&gt;</span><span style="color: red">&lt;definition&gt;<p id="ch2intro_6e"></a>A textual description of the functioning of the command or function.</p>&lt;/definition&gt;</span>&lt;/definition_list_item&gt;</span><span style="color: red">&lt;definition_list_item&gt;<span style="color: red">&lt;term&gt;EXAMPLES&lt;/term&gt;</span><span style="color: red">&lt;definition&gt;<p id="ch2intro_6f"></a>Some examples of common usage.</p>&lt;/definition&gt;</span>&lt;/definition_list_item&gt;</span><span style="color: red">&lt;definition_list_item&gt;<span style="color: red">&lt;term&gt;SEE ALSO&lt;/term&gt;</span><span style="color: red">&lt;definition&gt;<p id="ch2intro_70"></a>A list of related commands or functions.</p>&lt;/definition&gt;</span>&lt;/definition_list_item&gt;</span>&lt;/definition_list&gt;</span><p id="ch2intro_71"></a>Other sections may be present, but these are not well standardized across man pages. Common examples include: OPTIONS, EXIT STATUS, ENVIRONMENT, KNOWN BUGS, FILES, AUTHOR, REPORTING BUGS, HISTORY and COPYRIGHT.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   438
 
<p id="ch2intro_72"></a>These days virtually every Unix command line application comes with its man page, and many Unix users perceive a lack of man pages as a sign of low quality; indeed, some projects, such as Debian, go out of their way to write man pages for programs lacking one. Few alternatives to <span class="emphasis"><em>man</em></span> have enjoyed much popularity, with the possible exception of the GNU project's "info" system, an early and simple hypertext system.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   439
 
<p id="ch2intro_73"></a>However, the format of a single page for each application, the lack of classification within the sections and the relatively unsophisticated formatting facilities have motivated the development of alternative documentation systems, such as the previously mentioned "info" system.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   440
 
<p id="ch2intro_74"></a>Most Unix GUI applications (particularly those built using the GNOME and KDE development environments) now provide end-user documentation in HTML and include embedded HTML viewers such as yelp for reading the help within the application.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   441
 
<p id="ch2intro_75"></a>Usually the man pages are written in English. Translations into other languages can be also available on the system.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   442
 
<p id="ch2intro_76"></a>The default format of the man pages is troff, with either the macro package man (appearance oriented) or on some systems mdoc (semantic oriented). This makes it possible to typeset a man page to PostScript, PDF and various other formats for viewing or printing.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   443
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   444
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   445
 
<div class="section" title="4.3. info">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   446
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   447
 
<a name="id2983870"></a>4.3. info</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   448
 
<p id="ch2intro_77"></a><span class="emphasis"><em>info</em></span> is a software utility which forms a hypertextual, multipage documentation and help viewer working on a command line interface, useful when there is no GUI available.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   449
 
<p id="ch2intro_78"></a>The syntax is</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   450
 
<pre class="programlisting">$ info &lt;command_name&gt;</pre>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   451
 
<p id="ch2intro_79"></a><span class="emphasis"><em>info</em></span> processes info files, which are Texinfo formatted files, and presents the documentation as a tree, with simple commands to traverse the tree and to follow cross references. For instance</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   452
 
<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   453
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_7a"></a><span class="emphasis"><em>n</em></span> goes to the next page.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   454
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_7b"></a><span class="emphasis"><em>p</em></span> goes to the previous page.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   455
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_7c"></a><span class="emphasis"><em>u</em></span> goes to the upper page.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   456
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_7d"></a><span class="emphasis"><em>l</em></span> goes to the last(visited) node</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   457
 
<li class="listitem" style="list-style-type: *"><p id="ch2intro_7e"></a>To follow a cross reference, the cursor can be moved over a link (a word preceded by a <span style="color: red">&lt;title_reference&gt;*&lt;/title_reference&gt;</span>) and enter pressed.</p></li>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   458
 
</ul></div>&lt;/block_quote&gt;</span><p id="ch2intro_7f"></a>info was initially written for use with GNU/Linux and then ported to other Unix-like operating systems.</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   459
 
</div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   460
 
<div class="section" title="4.4. --help">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   461
 
<div class="titlepage"><div><div><h3 class="title">
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   462
 
<a name="id2983961"></a>4.4. --help</h3></div></div></div>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   463
 
<p id="ch2intro_80"></a>Most GNU commands support the --help, which gives a short explanation about how to use the command and a list of available options. Below is the output of this option with the <span class="emphasis"><em>cat</em></span> command:</p>
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   464
 
<pre class="programlisting">$ userprompt@host: cat --help
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   465
 
Usage: cat [OPTION] [FILE]...
672eaaab9204 Added some new html files that failed earlier during change from rst
amit@thunder
parents: 0
diff changeset 
   466
 
Concatenate FILE(s), or standard input, to standard output.
0
8083d21c0020 The first commit of all the required files for the review app
amit@thunder
parents:
diff changeset 
   467
 







1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   468


  -A, --show-all           equivalent to -vET













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   469


  -b, --number-nonblank    number nonempty output lines













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   470


  -e                       equivalent to -vE













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   471


  -E, --show-ends          display $ at end of each line













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   472


  -n, --number             number all output lines













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   473


  -s, --squeeze-blank      suppress repeated empty output lines













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   474


  -t                       equivalent to -vT













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   475


  -T, --show-tabs          display TAB characters as ^I













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   476


  -u                       (ignored)













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   477


  -v, --show-nonprinting   use ^ and M- notation, except for LFD and              TAB













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   478


  --help     display this help and exit













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   479


  --version  output version information and exit













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   480














672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   481


With no FILE, or when FILE is -, read standard input.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   482














672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   483


Examples:













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   484


  cat f - g  Output f's contents, then standard input, then g's           contents.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   485


  cat        Copy standard input to standard output.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   486














672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   487


Report bugs to &lt;bug-coreutils@gnu.org&gt;.</pre>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   488


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   489


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   490


<div class="section" title="5. Basic file handling">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   491


<div class="titlepage"><div><div><h2 class="title" style="clear: both">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   492


<a name="id2984014"></a>5. Basic file handling</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   493


<div class="section" title="5.1. cp">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   494


<div class="titlepage"><div><div><h3 class="title">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   495


<a name="id2984023"></a>5.1. cp</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   496


<p id="ch2intro_81"></a><span class="emphasis"><em>cp</em></span> is the command entered in a Unix shell to copy a file from one place to another, possibly on a different filesystem. The original file remains unchanged, and the new file may have the same or a different name.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   497


<div class="section" title="5.1.1. Usage">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   498


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   499


<a name="id2984040"></a>5.1.1. Usage</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   500


<p id="ch2intro_82"></a>To copy a file to another file:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   501


<pre class="programlisting">$ cp [ -f ] [ -H ] [ -i ] [ -p ][ -- ] SourceFile TargetFile</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   502


<p id="ch2intro_83"></a>To copy a file to a directory:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   503


<pre class="programlisting">$ cp [ -f ] [ -H ] [ -i ] [ -p ] [ -r | -R ] [ -- ] SourceFile ...              TargetDirectory</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   504


<p id="ch2intro_84"></a>To copy a directory to a directory:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   505


<pre class="programlisting">$ cp [ -f ] [ -H ] [ -i ] [ -p ] [ -- ] { -r | -R }













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   506


SourceDirectory ... TargetDirectory</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   507


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   508


<div class="section" title="5.1.2. Flags">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   509


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   510


<a name="id2984074"></a>5.1.2. Flags</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   511


<p id="ch2intro_85"></a><span class="emphasis"><em>-f</em></span> (force) – specifies removal of the target file if it cannot be opened for write operations. The removal precedes any copying performed by the cp command.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   512


<p id="ch2intro_86"></a><span class="emphasis"><em>-P</em></span> – makes the cp command copy symbolic links. The default is to follow symbolic links, that is, to copy files to which symbolic links point.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   513


<p id="ch2intro_87"></a><span class="emphasis"><em>-i</em></span> (interactive) – prompts you with the name of a file to be overwritten. This occurs if the TargetDirectory or TargetFile parameter contains a file with the same name as a file specified in the SourceFile or SourceDirectory parameter. If you enter y or the locale's equivalent of y, the cp command continues. Any other answer prevents the cp command from overwriting the file.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   514


<p id="ch2intro_88"></a><span class="emphasis"><em>-p</em></span> (preserve) – duplicates the following characteristics of each SourceFile/SourceDirectory in the corresponding TargetFile and/or TargetDirectory:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   515


<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   516


<li class="listitem" style="list-style-type: *"><p id="ch2intro_89"></a>The time of the last data modification and the time of the last access.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   517


<li class="listitem" style="list-style-type: *"><p id="ch2intro_8a"></a>The user ID and group ID (only if it has permissions to do this)</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   518


<li class="listitem" style="list-style-type: *"><p id="ch2intro_8b"></a>The file permission bits and the SUID and SGID bits.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   519


</ul></div>&lt;/block_quote&gt;</span><p id="ch2intro_8c"></a><span class="emphasis"><em>-R</em></span> (recursive) – copy directories (recursively copying all the contents)</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   520


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   521


<div class="section" title="5.1.3. Examples">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   522


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   523


<a name="id2984172"></a>5.1.3. Examples</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   524


<p id="ch2intro_8d"></a>To make a copy of a file in the current directory, enter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   525


<pre class="programlisting">$ cp prog.c prog.bak</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   526


<p id="ch2intro_8e"></a>This copies prog.c to prog.bak. If the prog.bak file does not already exist, the cp command creates it. If it does exist, the cp command replaces it with a copy of the prog.c file.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   527


<p id="ch2intro_8f"></a>To copy a file in your current directory into another directory, enter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   528


<pre class="programlisting">$ cp zaphod /home/books/hhgg</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   529


<p id="ch2intro_90"></a>This copies the jones file to /home/books/hhgg/zaphod.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   530


<p id="ch2intro_91"></a>To copy a file to a new file and preserve the modification date, time, and access control list associated with the source file, enter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   531


<pre class="programlisting">$ cp -p martin_luther_king martin_luther_king.jr</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   532


<p id="ch2intro_92"></a>This copies the <span class="emphasis"><em>martin_luther_king</em></span> file to the <span class="emphasis"><em>martin_luther_king.jr</em></span> file. Instead of creating the file with the current date and time stamp, the system gives the <span class="emphasis"><em>martin_luther_king.jr</em></span> file the same date and time as the <span class="emphasis"><em>martin_luther_king</em></span> file. The <span class="emphasis"><em>martin_luther_king.jr</em></span> file also inherits the <span class="emphasis"><em>martin_luther_king</em></span> file's access control protection.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   533


<p id="ch2intro_93"></a>To copy all the files in a directory to a new directory, enter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   534


<pre class="programlisting">$ cp /home/galactica/clients/* /home/hhgg/customers</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   535


<p id="ch2intro_94"></a>This copies only the files in the clients directory to the customers directory.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   536


<p id="ch2intro_95"></a>To copy a directory, including all its files and subdirectories, to another directory, enter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   537


<span style="color: red">&lt;block_quote&gt;<p id="ch2intro_96"></a>$ cp -R /home/hhgg/clients /home/hhgg/customers</p>&lt;/block_quote&gt;</span><p id="ch2intro_97"></a>This copies the clients directory, including all its files, subdirectories, and the files in those subdirectories, to the customers/clients directory.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   538


<p id="ch2intro_98"></a>To copy a specific set of files of any extension to another directory, enter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   539


<pre class="programlisting">$ cp zaphod arthur ford /home/hhgg/clients</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   540


<p id="ch2intro_99"></a>This copies the <span class="emphasis"><em>zaphod</em></span>, <span class="emphasis"><em>arthur</em></span>, and <span class="emphasis"><em>ford</em></span> files in your current working directory to the /home/hhgg/clients directory.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   541


<p id="ch2intro_9a"></a>To use pattern-matching characters to copy files, enter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   542


<pre class="programlisting">$ cp programs/*.py .</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   543


<p id="ch2intro_9b"></a>This copies the files in the programs directory that end with <span class="emphasis"><em>.py</em></span> to the current directory, signified by the single "." (dot). You must type a space between the <span class="emphasis"><em>py</em></span> and the final dot.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   544


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   545


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   546


<div class="section" title="5.2. mv">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   547


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   548


<a name="id2984334"></a>5.2. mv</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   549


<p id="ch2intro_9c"></a><span class="emphasis"><em>mv</em></span> (short for move) is a Unix command that moves one or more files or directories from one place to another. The original file is deleted, and the new file may have the same or a different name. If possible (i.e. when the original and new files are on the same file system), <span class="emphasis"><em>mv</em></span> will rename the file instead. Write permission is required on all directories being modified.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   550


<div class="section" title="5.2.1. Conflicting existing file">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   551


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   552


<a name="id2984358"></a>5.2.1. Conflicting existing file</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   553


<p id="ch2intro_9d"></a>In all cases, when a file is moved to have the name of an existing file (in the same directory), the existing file is deleted. If the existing file is not writable but is in a directory that is writable, then the mv command asks for confirmation if possible (i.e. if run from a terminal) before proceeding, unless the -f (force) option is used.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   554


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   555


<div class="section" title="5.2.2. Differences with copy and delete">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   556


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   557


<a name="id2984377"></a>5.2.2. Differences with copy and delete</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   558


<p id="ch2intro_9e"></a>Note that, usually, when moving files within the same volume, moving (and/or renaming) is not the same as simply copying and then deleting the original. When moving a file, the link is simply removed from the old parent directory and added to the new parent directory. However, the file itself is untouched (i.e. it has the same inodes and resides at the same place on the disk). For example, you cannot copy a file you cannot read, but you can move (and/or rename) it (provided you have write permission to its old and new parent directories). Also, suppose there is a non-empty directory you do not have write permission to. You cannot delete this directory (since you cannot delete its contents); but you can move (and/or rename) it. Also, since moving between filenames on a single volume does not involve copying, it is faster and does not place strain of lots of reads and writes on the disk. Moving files across different volumes, however, does necessitate copying and deleting.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   559


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   560


<div class="section" title="5.2.3. Examples">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   561


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   562


<a name="id2984423"></a>5.2.3. Examples</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   563


<pre class="programlisting">$ mv myfile mynewfilename    renames a file













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   564


$ mv myfile otherfilename    renames a file and deletes the existing            file "myfile"













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   565


$ mv myfile /myfile          moves 'myfile' from the current            directory to the root directory













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   566


$ mv myfile dir/myfile       moves 'myfile' to 'dir/myfile' relative            to the current directory













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   567


$ mv myfile dir              same as the previous command (the          filename is implied to be the same)













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   568


$ mv myfile dir/myfile2      moves 'myfile' to dir and renames it to            'myfile2'













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   569


$ mv foo bar baz dir         moves multiple files to directory dir













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   570


$ mv --help                  shows a very concise help about the                syntax of the command













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   571


$ man mv                     prints an extensive user manual for                'mv' in the terminal</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   572


<p id="ch2intro_9f"></a>In all cases, the file or files being moved or renamed can be a directory.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   573


<p id="ch2intro_a0"></a>Note that when the command is called with two arguments (as <span class="emphasis"><em>mv name1 name2</em></span> or <span class="emphasis"><em>mv name1 /dir/name2</em></span>), it can have three different effects, depending on whether <span class="emphasis"><em>name2</em></span> does not exist, is an existing file, or is an existing directory. If the user intends to refer to an existing directory, <span class="emphasis"><em>/.</em></span> (or in some Unix versions <span class="emphasis"><em>/</em></span> is sufficient) may be appended to the name to force the system to check this. To move a file to a new directory, the directory must be created first.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   574


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   575


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   576


<div class="section" title="5.3. rm">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   577


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   578


<a name="id2984483"></a>5.3. rm</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   579


<p id="ch2intro_a1"></a><span class="emphasis"><em>rm</em></span> (short for "remove") is one of several basic Unix command lines that operates on files. It is used to delete files from a filesystem. The data is not actually destroyed. Only the index listing where the file is stored is destroyed, and the storage is made available for reuse. There are undelete utilities that will attempt to reconstruct the index and can bring the file back if the parts were not reused.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   580


<p id="ch2intro_a2"></a>Here's example to remove a file named "foo" from a directory, here shown with the -i option:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   581


<pre class="programlisting">$ rm -i foo













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   582


remove foo? y</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   583


<div class="section" title="5.3.1. Options">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   584


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   585


<a name="id2984512"></a>5.3.1. Options</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   586


<p id="ch2intro_a3"></a>Common options that rm accepts include:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   587


<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   588


<li class="listitem" style="list-style-type: *"><p id="ch2intro_a4"></a><span class="emphasis"><em>-r</em></span>, which removes directories, removing the contents recursively beforehand (so as not to leave files without a directory to reside in) ("recursive")</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   589


<li class="listitem" style="list-style-type: *"><p id="ch2intro_a5"></a><span class="emphasis"><em>-i</em></span>, which asks for every deletion to be confirmed ("interactive")</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   590


<li class="listitem" style="list-style-type: *"><p id="ch2intro_a6"></a><span class="emphasis"><em>-f</em></span>, which ignores non-existent files and overrides any confirmation prompts ("force")</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   591


<li class="listitem" style="list-style-type: *"><p id="ch2intro_a7"></a><span class="emphasis"><em>-v</em></span>, which shows what is being removed as it happens ("verbose")</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   592


</ul></div>&lt;/block_quote&gt;</span><p id="ch2intro_a8"></a><span class="emphasis"><em>rm</em></span> is often aliased to "rm -i" so as to avoid accidental deletion of files. If a user still wishes to delete a large number of files without confirmation, they can manually cancel out the -i argument by adding the -f option (as the option specified later on the expanded command line "rm -i -f" takes precedence).</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   593


<p id="ch2intro_a9"></a><span class="emphasis"><em>rm -rf</em></span> (variously, rm -rf /, rm -rf <span style="color: red">&lt;title_reference&gt;*&lt;/title_reference&gt;</span>, and others) is frequently used in jokes and anecdotes about Unix disasters. The rm -rf variant of the command, if run by a superuser on the root directory, would cause the contents of every writable mounted filesystem on the computer to be deleted.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   594


<p id="ch2intro_aa"></a><span class="emphasis"><em>rm</em></span> is often used in conjunction with xargs to supply a list of files to delete:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   595


<pre class="programlisting">xargs rm &lt; filelist</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   596


<p id="ch2intro_ab"></a>When <span class="emphasis"><em>rm</em></span> is used on a symbolic link, it deletes the link, but does not affect the target of the link.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   597


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   598


<div class="section" title="5.3.2. Permissions">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   599


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   600


<a name="id2984613"></a>5.3.2. Permissions</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   601


<p id="ch2intro_ac"></a>Usually, on most filesystems, deleting a file requires write permission on the parent directory (and execute permission, in order to enter the directory in the first place). (Note that, confusingly for beginners, permissions on the file itself are irrelevant. However, GNU rm asks for confirmation if a write-protected file is to be deleted, unless the -f option is used.)</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   602


<p id="ch2intro_ad"></a>To delete a directory (with rm -r), one must delete all of its contents recursively. This requires that one must have read and write and execute permission to that directory (if it's not empty) and all non-empty subdirectories recursively (if there are any). The read permissions are needed to list the contents of the directory in order to delete them. This sometimes leads to an odd situation where a non-empty directory cannot be deleted because one doesn't have write permission to it and so cannot delete its contents; but if the same directory were empty, one would be able to delete it.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   603


<p id="ch2intro_ae"></a>If a file resides in a directory with the sticky bit set, then deleting the file requires one to be the owner of the file.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   604


</div>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   605


</div>













8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   606


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   607


<div class="section" title="6. Command Line Arguments">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   608


<div class="titlepage"><div><div><h2 class="title" style="clear: both">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   609


<a name="id2984653"></a>6. Command Line Arguments</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   610


<p id="ch2intro_af"></a>In computer command line interfaces, a command line argument is an argument sent to a program being called. In general, a program can take any number of command line arguments, which may be necessary for the program to run, or may even be ignored, depending on the function of that program.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   611


<p id="ch2intro_b0"></a>For example, in Unix and Unix-like environments, an example of a command-line argument is:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   612


<pre class="programlisting">rm file.s</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   613


<p id="ch2intro_b1"></a>"file.s" is a command line argument which tells the program rm to remove the file "file.s".</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   614


<p id="ch2intro_b2"></a>Programming languages such as C, C++ and Java allow a program to interpret the command line arguments by handling them as string parameters in the main function.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   615


<p id="ch2intro_b3"></a>A command line option or simply <span class="emphasis"><em>option</em></span> (also known as a command line parameter, flag, or a switch) is an indication by a user that a computer program should change its default output.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   616


<p id="ch2intro_b4"></a>Long options are introduced via "--", and are typically whole words. For example, <span class="emphasis"><em>ls --long --classify --all</em></span>. Arguments to long options are provided with "=", as <span class="emphasis"><em>ls --block-size=1024</em></span>. Some Unix programs use long options with single dashes, for example MPlayer as in <span class="emphasis"><em>mplayer -nosound</em></span>.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   617


<p id="ch2intro_b5"></a>Linux also uses "--" to terminate option lists. For example, an attempt to delete a file called <span class="emphasis"><em>-file1</em></span> by using <span class="emphasis"><em>rm -file1</em></span> may produce an error, since rm may interpret <span class="emphasis"><em>-file1</em></span> as a command line switch. Using <span class="emphasis"><em>rm -- -file1</em></span> removes ambiguity.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   618


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   619


<div class="section" title="7. Basic Text Processing">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   620


<div class="titlepage"><div><div><h2 class="title" style="clear: both">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   621


<a name="id2984746"></a>7. Basic Text Processing</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   622


<div class="section" title="7.1. head">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   623


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   624


<a name="id2984755"></a>7.1. head</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   625


<p id="ch2intro_b6"></a><span class="emphasis"><em>head</em></span> is a program on Unix and Unix-like systems used to display the first few lines of a text file or piped data. The command syntax is:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   626


<pre class="programlisting">$ head [options] &lt;file_name&gt;</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   627


<p id="ch2intro_b7"></a>By default, <span class="emphasis"><em>head</em></span> will print the first 10 lines of its input to the standard output. The number of lines printed may be changed with a command line option. The following example shows the first 20 lines of filename:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   628


<pre class="programlisting">$ head -n 20 filename</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   629


<p id="ch2intro_b8"></a>This displays the first 5 lines of all files starting with <span class="emphasis"><em>foo</em></span>:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   630


<pre class="programlisting">$ head -n 5 foo*</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   631


<p id="ch2intro_b9"></a>Some versions omit the n and just let you say -5.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   632


<div class="section" title="7.1.1. Flags">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   633


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   634


<a name="id2984806"></a>7.1.1. Flags</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   635


<pre class="programlisting">-c &lt;x number of bytes&gt; Copy first x number of bytes.</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   636


<p id="ch2intro_ba"></a>Other options: <span class="emphasis"><em>sed</em></span></p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   637


<p id="ch2intro_bb"></a>Many early versions of Unix did not have this command, and so documentation and books had <span class="emphasis"><em>sed</em></span> do this job:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   638


<pre class="programlisting">sed 5q foo</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   639


<p id="ch2intro_bc"></a>This says to print every line (implicit), and quit after the fifth.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   640


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   641


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   642


<div class="section" title="7.2. tail">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   643


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   644


<a name="id2984842"></a>7.2. tail</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   645


<p id="ch2intro_bd"></a><span class="emphasis"><em>tail</em></span> is a program on Unix and Unix-like systems used to display the last few lines of a text file or piped data.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   646


<p id="ch2intro_be"></a>The command-syntax is:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   647


<pre class="programlisting">$ tail [options] &lt;file_name&gt;</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   648


<p id="ch2intro_bf"></a>By default, <span class="emphasis"><em>tail</em></span> will print the last 10 lines of its input to the standard output. With command line options the number of lines printed and the printing units (lines, blocks or bytes) may be changed. The following example shows the last 20 lines of filename:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   649


<pre class="programlisting">$ tail -n 20 filename</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   650


<p id="ch2intro_c0"></a>This example shows the last 15 bytes of all files starting with <span class="emphasis"><em>foo</em></span>:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   651


<pre class="programlisting">$ tail -c 15 foo*</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   652


<p id="ch2intro_c1"></a>This example shows all lines of filename from the second line onwards:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   653


<pre class="programlisting">$ tail -n +2 filename</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   654


<p id="ch2intro_c2"></a>Using an older syntax (still used in Sun Solaris as the -n option is not supported), the last 20 lines and the last 50 bytes of filename can be shown with the following command:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   655


<pre class="programlisting">$ tail -20 filename













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   656


$ tail -50c filename</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   657


<p id="ch2intro_c3"></a>However this syntax is now obsolete and does not conform with the POSIX 1003.1-2001 standard. Even if still supported in current versions, when used with other options (like -f, see below), these switches could not work at all.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   658


<div class="section" title="7.2.1. File monitoring">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   659


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   660


<a name="id2984920"></a>7.2.1. File monitoring</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   661


<p id="ch2intro_c4"></a><span class="emphasis"><em>tail</em></span> has a special command line option <span class="emphasis"><em>-f</em></span> (follow) that allows a file to be monitored. Instead of displaying the last few lines and exiting, tail displays the lines and then monitors the file. As new lines are added to the file by another process, tail updates the display. This is particularly useful for monitoring log files. The following command will display the last 10 lines of messages and append new lines to the display as new lines are added to messages:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   662


<pre class="programlisting">$ tail -f /var/adm/messages</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   663


<p id="ch2intro_c5"></a>To interrupt tail while it is monitoring, break-in with <span class="emphasis"><em>Ctrl+C</em></span>. This command can be run "in the background" with &amp;, see job control.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   664


<p id="ch2intro_c6"></a>If you have a command's result to monitor, you can use the <span class="emphasis"><em>watch</em></span> command.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   665


</div>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   666


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   667


<div class="section" title="7.3. cut">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   668


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   669


<a name="id2984970"></a>7.3. cut</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   670


<p id="ch2intro_c7"></a>In computing, <span class="emphasis"><em>cut</em></span> is a Unix command line utility which is used to extract sections from each line of input — usually from a file.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   671


<p id="ch2intro_c8"></a>Extraction of line segments can typically be done by <span class="emphasis"><em>bytes (-b), characters (-c)</em></span>, or <span class="emphasis"><em>fields (-f)</em></span> separated by a <span class="emphasis"><em>delimiter (-d — the tab character by default)</em></span>. A range must be provided in each case which consists of one of N, N-M, N- (N to the end of the line), or -M (beginning of the line to M), where N and M are counted from 1 (there is no zeroth value). Since version 6, an error is thrown if you include a zeroth value. Prior to this the value was ignored and assumed to be 1.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   672


<p id="ch2intro_c9"></a>Assuming a file named file containing the lines:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   673


<pre class="programlisting">foo:bar:baz:qux:quux













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   674


one:two:three:four:five:six:seven













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   675


alpha:beta:gamma:delta:epsilon:zeta:eta:teta:iota:kappa:lambda:mu</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   676


<p id="ch2intro_ca"></a>To output the fourth through tenth characters of each line:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   677


<pre class="programlisting">$ cut -c 4-10 file</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   678


<p id="ch2intro_cb"></a>This gives the output:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   679


<pre class="programlisting">:bar:ba













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   680


:two:th













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   681


ha:beta</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   682


<p id="ch2intro_cc"></a>To output the fifth field through the end of the line of each line using the colon character as the field delimiter:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   683


<pre class="programlisting">$ cut -d : -f 5- file</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   684


<p id="ch2intro_cd"></a>This gives the output:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   685


<pre class="programlisting">quux













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   686


five:six:seven













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   687


epsilon:zeta:eta:teta:iota:kappa:lambda:mu</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   688


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   689


<div class="section" title="7.4. paste">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   690


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   691


<a name="id2985055"></a>7.4. paste</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   692


<p id="ch2intro_ce"></a><span class="emphasis"><em>paste</em></span> is a Unix command line utility which is used to join files horizontally (parallel merging) by outputting lines consisting of the sequentially corresponding lines of each file specified, separated by tabs, to the standard output. It is effectively the horizontal equivalent to the utility <span class="emphasis"><em>cat</em></span> command which operates on the vertical plane of two or more files.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   693


<p id="ch2intro_cf"></a>To paste several columns of data together into the file <span class="emphasis"><em>www</em></span> from files <span class="emphasis"><em>who</em></span>, <span class="emphasis"><em>where</em></span>, and <span class="emphasis"><em>when</em></span>:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   694


<pre class="programlisting">$ paste who where when &gt; www</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   695


<p id="ch2intro_d0"></a>If the files contain:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   696


<table summary="paste" border="1"><colgroup>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   697


<col width="11">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   698


<col width="12">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   699


<col width="12">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   700


</colgroup></table>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   701


<p id="ch2intro_dd"></a>This creates the file named <span class="emphasis"><em>www</em></span> containing:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   702


<pre class="programlisting">Batman            GothamCity       January 3













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   703


Trillian          Andromeda        February 4













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   704


Jeeves            London           March 19</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   705


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   706


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   707


<div class="section" title="8. Shell Meta Characters">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   708


<div class="titlepage"><div><div><h2 class="title" style="clear: both">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   709


<a name="id2985190"></a>8. Shell Meta Characters</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   710


<p id="ch2intro_de"></a>Unix recognizes certain special characters, called "meta characters," as command directives. The shell meta characters are recognized anywhere they appear in the command line, even if they are not surrounded by blank space. For that reason, it is safest to only use the characters A-Z, a-z, 0-9, and the period, dash, and underscore characters when naming files and directories on Unix. If your file or directory has a shell meta character in the name, you will find it difficult to use the name in a shell command.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   711


<p id="ch2intro_df"></a>The shell meta characters include:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   712


<p id="ch2intro_e0"></a>/ &lt; &gt; ! $ % ^ &amp; * | { } [ ] " ' ` ~ ;</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   713


<p id="ch2intro_e1"></a>Different shells may differ in the meta characters recognized.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   714


<p id="ch2intro_e2"></a>As an example,</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   715


<pre class="programlisting">$ ls file.*</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   716


<p id="ch2intro_e3"></a>run on a directory containing the files file, file.c, file.lst, and myfile would list the files file.c and file.lst. However,:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   717


<pre class="programlisting">$ ls file.?</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   718


<p id="ch2intro_e4"></a>run on the same directory would only list file.c because the ? only matches one character, no more, no less. This can save you a great deal of typing time. For example, if there is a file called california_cornish_hens_with_wild_rice and no other files whose names begin with 'c', you could view the file without typing the whole name by typing this:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   719


<pre class="programlisting">$ more c*</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   720


<p id="ch2intro_e5"></a>because the c* matches that long file name.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   721


<p id="ch2intro_e6"></a>Filenames containing metacharacters can pose many problems and should never be intentionally created. If you do find that you've created a file with metacharacters, and you would like to remove it, you have three options. You may use wildcards to match metacharacter, use the  to directly enter the filename, or put the command in double quotes (except in the case of double quotes within the file name, these must be captured with one of the first two methods). For example, deleting a file named <span style="color: red">&lt;title_reference&gt;"``*`|more&lt;/title_reference&gt;</span>"` can be accomplished with:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   722


<pre class="programlisting">$ rm ??more</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   723


<p id="ch2intro_e7"></a>or:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   724


<pre class="programlisting">$ rm $\backslash$*$\backslash$|more</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   725


<p id="ch2intro_e8"></a>or:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   726


<pre class="programlisting">$ rm ''*|more''</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   727


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   728


<div class="section" title="9. Looking At Files">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   729


<div class="titlepage"><div><div><h2 class="title" style="clear: both">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   730


<a name="id2985297"></a>9. Looking At Files</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   731


<div class="section" title="9.1. cat">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   732


<div class="titlepage"><div><div><h3 class="title">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   733


<a name="id2985305"></a>9.1. cat</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   734


<p id="ch2intro_e9"></a>The <span class="emphasis"><em>cat</em></span> command is a standard Unix program used to concatenate and display files. The name is from "catenate", a synonym of <span class="emphasis"><em>concatenate</em></span>.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   735


<p id="ch2intro_ea"></a>The Single Unix Specification specifies the behavior that the contents of each of the files given in sequence as arguments will be written to the standard output in the same sequence, and mandates one option, -u, where each byte is printed as it is read.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   736


<p id="ch2intro_eb"></a>If the filename is specified as -, then <span class="emphasis"><em>cat</em></span> will read from standard input at that point in the sequence. If no files are specified, <span class="emphasis"><em>cat</em></span> will read from standard input entered.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   737


<div class="section" title="9.1.1. Jargon File Definition">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   738


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   739


<a name="id2985349"></a>9.1.1. Jargon File Definition</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   740


<p id="ch2intro_ec"></a>The Jargon File version 4.4.7 lists this as the definition of <span class="emphasis"><em>cat</em></span>:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   741


<pre class="programlisting">1. To spew an entire file to the screen or some other output sink without













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   742


     pause (syn. blast).













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   743














672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   744


2. By extension, to dump large amounts of data at an unprepared target or













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   745


     with no intention of browsing it carefully. Usage: considered silly.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   746


     Rare outside Unix sites. See also dd, BLT.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   747














672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   748


     Among Unix fans, *cat(1)* is considered an excellent example of













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   749


     user-interface design, because it delivers the file contents without













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   750


     such verbosity as spacing or headers between the files, and because













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   751


     it does not require the files to consist of lines of text, but works













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   752


     with any sort of data.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   753














672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   754


     Among Unix critics, *cat(1)* is considered the canonical example of













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   755


     bad user-interface design, because of its woefully unobvious name.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   756


     It is far more often used to blast a single file to standard output













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   757


     than to concatenate two or more files. The name cat for the former













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   758


     operation is just as unintuitive as, say, LISP's cdr.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   759














672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   760


     Of such oppositions are holy wars made...</pre>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   761


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   762


<div class="section" title="9.1.2. Useless Use of 'cat'">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   763


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   764


<a name="id2985388"></a>9.1.2. Useless Use of 'cat'</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   765


<p id="ch2intro_ed"></a>UUOC (from comp.unix.shell on Usenet) stands for “Useless Use of cat”. As it is observed on <span class="emphasis"><em>comp.unix.shell</em></span>, “The purpose of cat is to concatenate (or 'catenate') files. If it's only one file, concatenating it with nothing at all is a waste of time, and costs you a process.”</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   766


<p id="ch2intro_ee"></a>Nevertheless one sees people doing:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   767


<pre class="programlisting">$ cat file | some_command and its args ...</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   768


<p id="ch2intro_ef"></a>instead of the equivalent and cheaper:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   769


<pre class="programlisting">&lt;file some_command and its args ...</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   770


<p id="ch2intro_f0"></a>or (equivalently and more classically):</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   771


<pre class="programlisting">some_command and its args ... &lt;file</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   772


<p id="ch2intro_f1"></a>Since 1995, occasional awards for UUOC have been given out. The activity of fixing instances of UUOC is sometimes called 'demoggification'.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   773


<p id="ch2intro_f2"></a>Amongst many, it is still considered safer to use <span class="emphasis"><em>cat</em></span> for such cases given that the &lt; and &gt; keys are next to each other in many popular keyboard mappings. While the risk might be low, the impact of using &gt; instead of &lt; can be high and prohibitive.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   774


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   775


<div class="section" title="9.1.3. zcat">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   776


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   777


<a name="id2985457"></a>9.1.3. zcat</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   778


<p id="ch2intro_f3"></a><span class="emphasis"><em>zcat</em></span> is a Unix program similar to <span class="emphasis"><em>cat</em></span>, that decompresses individual files and concatenates them to standard output. Traditionally <span class="emphasis"><em>zcat</em></span> operated on files compressed by compress but today it is usually able to operate on <span class="emphasis"><em>gzip</em></span> or even <span class="emphasis"><em>bzip2</em></span> archives. On such systems, it is equivalent to <span class="emphasis"><em>gunzip -c</em></span></p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   779


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   780


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   781


<div class="section" title="9.2. more">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   782


<div class="titlepage"><div><div><h3 class="title">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   783


<a name="id2985493"></a>9.2. more</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   784


<p id="ch2intro_f4"></a>In computing, <span class="emphasis"><em>more</em></span> is a command to view (but not modify) the contents of a text file one screen at a time (terminal pager). It is available on Unix and Unix-like systems, DOS, OS/2 and Microsoft Windows. Programs of this sort are called pagers.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   785


<div class="section" title="9.2.1. Usage">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   786


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   787


<a name="id2985513"></a>9.2.1. Usage</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   788


<p id="ch2intro_f5"></a>The command-syntax is:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   789


<pre class="programlisting">$ more [options] [file_name]</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   790


<p id="ch2intro_f6"></a>If no file name is provided, <span class="emphasis"><em>more</em></span> looks for input from stdin.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   791


<p id="ch2intro_f7"></a>Once <span class="emphasis"><em>more</em></span> has obtained input, it displays as much as can fit on the current screen and waits for user input to advance, with the exception that a form feed (^L) will also cause <span class="emphasis"><em>more</em></span> to wait at that line, regardless of the amount of text on the screen. In the lower-left corner of the screen is displayed the text "--More--" and a percentage, representing the percent of the file that <span class="emphasis"><em>more</em></span> has paged through. (This percentage includes the text displayed on the current screen.) When <span class="emphasis"><em>more</em></span> reaches the end of a file (100%) it exits. The most common methods of navigating through a file are <span class="emphasis"><em>Enter</em></span>, which advances the output by one line, and <span class="emphasis"><em>Space</em></span>, which advances the output by one screen.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   792


<p id="ch2intro_f8"></a>There are also other commands that can be used while navigating through the document; consult <span class="emphasis"><em>more</em></span>'s <span class="emphasis"><em>man</em></span> page for more details.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   793


<p id="ch2intro_f9"></a><span class="emphasis"><em>Options</em></span> are typically entered before the file name, but can also be entered in the environment variable <span class="emphasis"><em>$MORE</em></span>. Options entered in the actual command line will override those entered in the <span class="emphasis"><em>$MORE</em></span> environment variable. Available options may vary between Unix systems.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   794


</div>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   795


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   796


<div class="section" title="9.3. less">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   797


<div class="titlepage"><div><div><h3 class="title">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   798


<a name="id2985608"></a>9.3. less</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   799


<p id="ch2intro_fa"></a><span class="emphasis"><em>less</em></span> is a terminal pager program on Unix, Windows and Unix-like systems used to view (but not change) the contents of a text file one screen at a time. It is similar to <span class="emphasis"><em>more</em></span>, but has the extended capability of allowing both forward and backward navigation through the file. Unlike most Unix text editors/viewers, <span class="emphasis"><em>less</em></span> does not need to read the entire file before starting, resulting in faster load times with large files.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   800


<div class="section" title="9.3.1. Usage">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   801


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   802


<a name="id2985637"></a>9.3.1. Usage</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   803


<p id="ch2intro_fb"></a><span class="emphasis"><em>less</em></span> can be invoked with options to change its behaviour, for example, the number of lines to display on the screen. A few options vary depending on the operating system. While <span class="emphasis"><em>less</em></span> is displaying the file, various commands can be used to navigate through the file. These commands are based on those used by both <span class="emphasis"><em>more</em></span> and <span class="emphasis"><em>vi</em></span>. It is also possible to search for character patterns in the file.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   804


<p id="ch2intro_fc"></a>By default, <span class="emphasis"><em>less</em></span> displays the contents of the file to the standard output (one screen at a time). If the file name argument is omitted, it displays the contents from standard input (usually the output of another command through a pipe). If the output is redirected to anything other than a terminal, for example a pipe to another command, less behaves like cat.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   805


<p id="ch2intro_fd"></a>The command-syntax is:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   806


<pre class="programlisting">$ less [options] file_name</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   807


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   808


<div class="section" title="9.3.2. Frequently Used Options">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   809


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   810


<a name="id2985691"></a>9.3.2. Frequently Used Options</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   811


<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   812


<li class="listitem" style="list-style-type: *"><p id="ch2intro_fe"></a>-g: Highlights just the current match of any searched string.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   813


<li class="listitem" style="list-style-type: *"><p id="ch2intro_ff"></a>-I: Case-insensitive searches.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   814


<li class="listitem" style="list-style-type: *"><p id="ch2intro_100"></a>-M: Shows more detailed prompt, including file position.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   815


<li class="listitem" style="list-style-type: *"><p id="ch2intro_101"></a>-N: Shows line numbers (useful for source code viewing).</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   816


<li class="listitem" style="list-style-type: *"><p id="ch2intro_102"></a>-S: Disables line wrap ("chop long lines"). Long lines can be seen by side scrolling.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   817


<li class="listitem" style="list-style-type: *"><p id="ch2intro_103"></a>-?: Shows help.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   818


</ul></div>&lt;/block_quote&gt;</span>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   819


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   820


<div class="section" title="9.3.3. Frequently Used Commands">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   821


<div class="titlepage"><div><div><h4 class="title">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   822


<a name="id2985743"></a>9.3.3. Frequently Used Commands</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   823


<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   824


<li class="listitem" style="list-style-type: *"><p id="ch2intro_104"></a>[Arrows]/[Page Up]/[Page Down]/[Home]/[End]: Navigation.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   825


<li class="listitem" style="list-style-type: *"><p id="ch2intro_105"></a>[Space bar]: Next page.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   826


<li class="listitem" style="list-style-type: *"><p id="ch2intro_106"></a>b: Previous page.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   827


<li class="listitem" style="list-style-type: *"><p id="ch2intro_107"></a>ng: Jump to line number n. Default is the start of the file.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   828


<li class="listitem" style="list-style-type: *"><p id="ch2intro_108"></a>nG: Jump to line number n. Default is the end of the file.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   829


<li class="listitem" style="list-style-type: *"><p id="ch2intro_109"></a>/pattern: Search for pattern. Regular expressions can be used.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   830


<li class="listitem" style="list-style-type: *"><p id="ch2intro_10a"></a>'^ or g: Go to start of file.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   831


<li class="listitem" style="list-style-type: *"><p id="ch2intro_10b"></a>'$ or G: Go to end of file.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   832


<li class="listitem" style="list-style-type: *"><p id="ch2intro_10c"></a>s: Save current content (got from another program like grep) in a file.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   833


<li class="listitem" style="list-style-type: *"><p id="ch2intro_10d"></a>=: File information.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   834


<li class="listitem" style="list-style-type: *"><p id="ch2intro_10e"></a>h: Help.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   835


<li class="listitem" style="list-style-type: *"><p id="ch2intro_10f"></a>q: Quit.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   836


</ul></div>&lt;/block_quote&gt;</span>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   837


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   838


<div class="section" title="9.3.4. Examples">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   839


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   840


<a name="id2985832"></a>9.3.4. Examples</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   841


<pre class="programlisting">$ less -M readme.txt                     #Read "readme.txt."













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   842


$ less +F /var/log/mail.log              #Follow mode for log













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   843


$ file * | less                          #Easier file analysis.













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   844


$ grep -i void *.c | less -I -p void     #Case insensitive search                                                         for "void" in all .c files</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   845


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   846


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   847


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   848


<div class="section" title="10. Directory Structure">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   849


<div class="titlepage"><div><div><h2 class="title" style="clear: both">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   850


<a name="id2985848"></a>10. Directory Structure</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   851


<p id="ch2intro_110"></a>In the File Hierarchy Standard (FHS) all files and directories appear under the root directory "/", even if they are stored on different physical devices. Note however that some of these directories may or may not be present on a Unix system depending on whether certain subsystems, such as the X Window System, are installed.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   852


<p id="ch2intro_111"></a>The majority of these directories exist in all UNIX operating systems and are generally used in much the same way; however, the descriptions here are those used specifically for the FHS, and are not considered authoritative for platforms other than Linux.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   853


<table summary="Directory Structure" border="1"><colgroup>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   854


<col width="15">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   855


<col width="48">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   856


</colgroup></table>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   857


<div class="section" title="10.1. man hier">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   858


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   859


<a name="id2986117"></a>10.1. man hier</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   860


<p id="ch2intro_136"></a>This is the manual page on the UNIX filesystem. The syntax for this is:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   861


<pre class="programlisting">$ man hier</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   862


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   863


<div class="section" title="10.2. ls -l">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   864


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   865


<a name="id2986133"></a>10.2. ls -l</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   866


<p id="ch2intro_137"></a>Shows you huge amounts of information (permissions, owners, size, and when last modified) for folders and files. The syntax is</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   867


<pre class="programlisting">$ ls -l</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   868


<p id="ch2intro_138"></a>This can be done after entering the required directory.</p>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   869


</div>













8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   870


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   871


<div class="section" title="11. Permissions and Ownership">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   872


<div class="titlepage"><div><div><h2 class="title" style="clear: both">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   873


<a name="id2986156"></a>11. Permissions and Ownership</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   874


<div class="section" title="11.1. chmod">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   875


<div class="titlepage"><div><div><h3 class="title">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   876


<a name="id2986165"></a>11.1. chmod</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   877


<p id="ch2intro_139"></a>The <span class="emphasis"><em>chmod</em></span> command (abbreviated from 'change mode') is a shell command and C language function in Unix and Unix-like environments. When executed, it can change file system modes of files and directories. The modes include permissions and special modes.A chmod command first appeared in AT&amp;T Unix version 1, and is still used today on Unix-like machines.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   878


<div class="section" title="11.1.1. Usage">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   879


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   880


<a name="id2986191"></a>11.1.1. Usage</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   881


<p id="ch2intro_13a"></a>The <span class="emphasis"><em>chmod</em></span> command options are specified like this:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   882


<pre class="programlisting">$ chmod [options] mode[,mode] file1 [file2 ...]</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   883


<p id="ch2intro_13b"></a>To view what the permissions currently are, type:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   884


<pre class="programlisting">$ ls -l file</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   885


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   886


<div class="section" title="11.1.2. Command line options">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   887


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   888


<a name="id2986219"></a>11.1.2. Command line options</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   889


<p id="ch2intro_13c"></a>The <span class="emphasis"><em>chmod</em></span> command has a number of command line options that affect its behavior. The most common options are:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   890


<span style="color: red">&lt;block_quote&gt;<div class="itemizedlist"><ul class="itemizedlist" type="*">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   891


<li class="listitem" style="list-style-type: *"><p id="ch2intro_13d"></a>-R: Changes the modes of directories and files recursively</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   892


<li class="listitem" style="list-style-type: *"><p id="ch2intro_13e"></a>-v: Verbose mode; lists all files as they are being processed</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   893


</ul></div>&lt;/block_quote&gt;</span><div class="section" title="11.1.2.1. Symbolic modes">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   894


<div class="titlepage"><div><div><h5 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   895


<a name="id2986255"></a>11.1.2.1. Symbolic modes</h5></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   896


<p id="ch2intro_13f"></a>To the <span class="emphasis"><em>chmod</em></span> utility, all permissions and special modes are represented by its mode parameter. One way to adjust the mode of files or directories is to specify a symbolic mode. The symbolic mode is composed of three components, which are combined to form a single string of text:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   897


<pre class="programlisting">$ chmod [references][operator][modes] file1 ...</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   898


<p id="ch2intro_140"></a>The references (or classes) are used to distinguish the users to whom the permissions apply. If no references are specified it defaults to “all” but modifies only the permissions allowed by the umask. The references are represented by one or more of the following letters:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   899


<table summary="Symbolic modes" border="1"><colgroup>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   900


<col width="14">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   901


<col width="8">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   902


<col width="45">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   903


</colgroup></table>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   904


<p id="ch2intro_150"></a>The <span class="emphasis"><em>chmod</em></span> program uses an operator to specify how the modes of a file should be adjusted. The following operators are accepted:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   905


<table summary="Symbolic modes" border="1"><colgroup>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   906


<col width="14">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   907


<col width="54">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   908


</colgroup></table>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   909


<p id="ch2intro_157"></a>The modes indicate which permissions are to be granted or taken away from the specified classes. There are three basic modes which correspond to the basic permissions:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   910


<table summary="Symbolic modes" border="1"><colgroup>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   911


<col width="5">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   912


<col width="14">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   913


<col width="48">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   914


</colgroup></table>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   915


<p id="ch2intro_16d"></a>The combination of these three components produces a string that is understood by the chmod command. Multiple changes can be specified by separating multiple symbolic modes with commas.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   916


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   917


<div class="section" title="11.1.2.2. Symbolic examples">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   918


<div class="titlepage"><div><div><h5 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   919


<a name="id2986802"></a>11.1.2.2. Symbolic examples</h5></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   920


<p id="ch2intro_16e"></a>Add the 'read' and 'write' permissions to the 'user' and 'group' classes of a directory:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   921


<pre class="programlisting">$ chmod ug+rw mydir













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   922


$ ls -ld mydir













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   923


drw-rw----   2 starwars  yoda  96 Dec 8 12:53 mydir</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   924


<p id="ch2intro_16f"></a>For a file, remove <span class="emphasis"><em>write</em></span> permissions for all classes:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   925


<pre class="programlisting">$ chmod a-w myfile













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   926


$ ls -l myfile













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   927


-r-xr-xr-x   2 starwars  yoda 96 Dec 8 12:53 myfile</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   928


<p id="ch2intro_170"></a>Set the permissions for the <span class="emphasis"><em>u*ser and the *g*roup to read and execute only (no write permission) on *mydir</em></span>.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   929


<pre class="programlisting">$ chmod ug=rx mydir













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   930


$ ls -ld mydir













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   931


dr-xr-x---   2 starwars  yoda 96 Dec 8 12:53 mydir</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   932


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   933


<div class="section" title="11.1.2.3. Octal numbers">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   934


<div class="titlepage"><div><div><h5 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   935


<a name="id2986842"></a>11.1.2.3. Octal numbers</h5></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   936


<p id="ch2intro_171"></a>The <span class="emphasis"><em>chmod</em></span> command also accepts three and four-digit octal numbers representing modes. Using a three-digit octal number to set the modes of a file named myfile :</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   937


<pre class="programlisting">$ chmod 664 myfile













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   938


$ ls -l myfile













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   939


-rw-rw-r--  1   57 Jul  3 10:13  myfile</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   940


<p id="ch2intro_172"></a>Since the <span class="emphasis"><em>setuid</em></span>, <span class="emphasis"><em>setgid</em></span> and <span class="emphasis"><em>sticky</em></span> bits are not set, this is equivalent to:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   941


<pre class="programlisting">$ chmod 0664 myfile</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   942


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   943


<div class="section" title="11.1.2.4. Special modes">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   944


<div class="titlepage"><div><div><h5 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   945


<a name="id2986882"></a>11.1.2.4. Special modes</h5></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   946


<p id="ch2intro_173"></a>The <span class="emphasis"><em>chmod</em></span> command is also capable of changing the additional permissions or special modes of a file or directory. The symbolic modes use <span class="strong"><strong>s</strong></span> to represent the <span class="emphasis"><em>setuid</em></span> and <span class="emphasis"><em>setgid</em></span> modes, and <span class="strong"><strong>t</strong></span> to represent the sticky mode. The modes are only applied to the appropriate classes, regardless of whether or not other classes are specified.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   947


<p id="ch2intro_174"></a>Most operating systems support the specification of special modes using octal modes, but some do not. On these systems, only the symbolic modes can be used.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   948


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   949


</div>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   950


</div>













8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   951


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   952


<div class="section" title="12. Redirection and Piping">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   953


<div class="titlepage"><div><div><h2 class="title" style="clear: both">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   954


<a name="id2986929"></a>12. Redirection and Piping</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   955


<p id="ch2intro_175"></a>In computing, <span class="emphasis"><em>redirection</em></span> is a function common to most command-line interpreters, including the various Unix shells that can redirect standard streams to user-specified locations.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   956


<p id="ch2intro_176"></a>Programs do redirection with the <span class="emphasis"><em>dup2(2)</em></span> system call, or its less-flexible but higher-level stdio analogues, <span class="emphasis"><em>freopen(3)</em></span> and <span class="emphasis"><em>popen(3)</em></span>.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   957


<div class="section" title="12.1. Redirecting standard input and standard output">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   958


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   959


<a name="id2986966"></a>12.1. Redirecting standard input and standard output</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   960


<p id="ch2intro_177"></a>Redirection is usually implemented by placing certain characters between commands. Typically, the syntax of these characters is as follows:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   961


<pre class="programlisting">$ command1 &gt; file1</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   962


<p id="ch2intro_178"></a>executes <span class="emphasis"><em>command1</em></span>, placing the output in file1. Note that this will truncate any existing data in <span class="emphasis"><em>file1</em></span>. To append output to the end of the file, use the &gt;&gt; operator.:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   963


<pre class="programlisting">$ command1 &lt; file1</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   964


<p id="ch2intro_179"></a>executes <span class="emphasis"><em>command1</em></span>, using <span class="emphasis"><em>file1</em></span> as the source of input (as opposed to the keyboard).:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   965


<pre class="programlisting">$ command1 &lt; infile &gt; outfile</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   966


<p id="ch2intro_17a"></a>combines the two capabilities: <span class="emphasis"><em>command1</em></span> reads from <span class="emphasis"><em>infile</em></span> and writes to <span class="emphasis"><em>outfile</em></span></p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   967


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   968


<div class="section" title="12.2. Piping">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   969


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   970


<a name="id2987035"></a>12.2. Piping</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   971


<p id="ch2intro_17b"></a>Programs can be run together such that one program reads the output from another with no need for an explicit intermediate file:













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   972


A pipeline of three programs run on a text terminal:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   973


<pre class="programlisting">$ command1 | command2</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   974


<p id="ch2intro_17c"></a>executes <span class="emphasis"><em>command1</em></span>, using its output as the input for <span class="emphasis"><em>command2</em></span> (commonly called piping, since the "|" character is known as a "pipe").</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   975


<p id="ch2intro_17d"></a>This is equivalent to using two redirects and a temporary file:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   976


<pre class="programlisting">$ command1 &gt; tempfile













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   977


$ command2 &lt; tempfile













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   978


$ rm tempfile</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   979


<p id="ch2intro_17e"></a>A good example for command piping is combining <span class="emphasis"><em>echo</em></span> with another command to achieve something interactive in a non-interactive shell, e.g.:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   980


<pre class="programlisting">$ echo -e "user\npass" | ftp localhost</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   981


<p id="ch2intro_17f"></a>This runs the ftp client with input user, press return, then pass.</p>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




   982


</div>








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   983


<div class="section" title="12.3. Redirecting to and from the standard file handles">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   984


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   985


<a name="id2987096"></a>12.3. Redirecting to and from the standard file handles</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   986


<p id="ch2intro_180"></a>In Unix shells derived from the original Bourne shell, the first two actions can be further modified by placing a number (the file descriptor) immediately before the character; this will affect which stream is used for the redirection. The Unix standard I/O streams are:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   987


<table summary="Redirecting to and from the standard file handles" border="1"><colgroup>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   988


<col width="12">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   989


<col width="13">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   990


<col width="24">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   991


</colgroup></table>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   992


<p id="ch2intro_18d"></a>For example:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   993


<pre class="programlisting">$ command1 2&gt; file1</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   994


<p id="ch2intro_18e"></a>executes <span class="emphasis"><em>command1</em></span>, directing the standard error stream to <span class="emphasis"><em>file1</em></span>.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   995


<p id="ch2intro_18f"></a>In shells derived from <span class="emphasis"><em>csh</em></span> (the C shell), the syntax instead appends the &amp; character to the redirect characters, thus achieving a similar result.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   996


<p id="ch2intro_190"></a>Another useful capability is to redirect one standard file handle to another. The most popular variation is to merge standard error into standard output so error messages can be processed together with (or alternately to) the usual output. Example:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   997


<pre class="programlisting">$ find / -name .profile &gt; results 2&gt;&amp;1</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   998


<p id="ch2intro_191"></a>will try to find all files named <span class="emphasis"><em>.profile</em></span>. Executed without redirection, it will output hits to <span class="emphasis"><em>stdout</em></span> and errors (e.g. for lack of privilege to traverse protected directories) to <span class="emphasis"><em>stderr</em></span>. If standard output is directed to file results, error messages appear on the console. To see both hits and error messages in file results, merge <span class="emphasis"><em>stderr</em></span> (handle 2) into <span class="emphasis"><em>stdout</em></span> (handle 1) using 2&gt;&amp;1 .</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




   999


<p id="ch2intro_192"></a>It's possible use 2&gt;&amp;1 before "&gt;" but it doesn't work. In fact, when the interpreter reads 2&gt;&amp;1, it doesn't know yet where standard output is redirected and then standard error isn't merged.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1000


<p id="ch2intro_193"></a>If the merged output is to be piped into another program, the file merge sequence 2&gt;&amp;1 must precede the pipe symbol, thus:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1001


<pre class="programlisting">$ find / -name .profile 2&gt;&amp;1 | less</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1002


<p id="ch2intro_194"></a>A simplified form of the command:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1003


<pre class="programlisting">$ command &gt; file 2&gt;&amp;1</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1004


<p id="ch2intro_195"></a>is:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1005


<pre class="programlisting">$ command &amp;&gt;file</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1006


<p id="ch2intro_196"></a>or:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1007


<pre class="programlisting">$command &gt;&amp;file</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1008


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1009


<div class="section" title="12.4. Chained pipelines">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1010


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1011


<a name="id2987301"></a>12.4. Chained pipelines</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1012


<p id="ch2intro_197"></a>The redirection and piping tokens can be chained together to create complex commands. For example:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1013


<pre class="programlisting">$ ls | grep '\.sh' | sort &gt; shlist</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1014


<p id="ch2intro_198"></a>lists the contents of the current directory, where this output is filtered to only contain lines which contain <span class="emphasis"><em>.sh</em></span>, sort this resultant output lexicographically, and place the final output in <span class="emphasis"><em>shlist</em></span>. This type of construction is used very commonly in shell scripts and batch files.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1015


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1016


<div class="section" title="12.5. Redirect to multiple outputs">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1017


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1018


<a name="id2987335"></a>12.5. Redirect to multiple outputs</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1019


<p id="ch2intro_199"></a>The standard command <span class="emphasis"><em>tee</em></span> can redirect output from a command to several destinations.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1020


<pre class="programlisting">$ ls -lrt | tee xyz</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1021


<p id="ch2intro_19a"></a>This directs the file list output to both standard output as well as to the file <span class="emphasis"><em>xyz</em></span>.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1022


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1023


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1024


<div class="section" title="13. More Text Processing">








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




  1025


<div class="titlepage"><div><div><h2 class="title" style="clear: both">








1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1026


<a name="id2987365"></a>13. More Text Processing</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1027


<div class="section" title="13.1. grep">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1028


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1029


<a name="id2987374"></a>13.1. grep</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1030


<p id="ch2intro_19b"></a><span class="emphasis"><em>grep</em></span> is a command line text search utility originally written for Unix. The name is taken from the first letters in <span class="emphasis"><em>global / regular expression / print</em></span>, a series of instructions for the <span class="emphasis"><em>ed</em></span> text editor. The <span class="emphasis"><em>grep</em></span> command searches files or standard input globally for lines matching a given regular expression, and prints them to the program's standard output.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1031


<div class="section" title="13.1.1. Usage">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1032


<div class="titlepage"><div><div><h4 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1033


<a name="id2987405"></a>13.1.1. Usage</h4></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1034


<p id="ch2intro_19c"></a>This is an example of a common <span class="emphasis"><em>grep</em></span> usage:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1035


<pre class="programlisting">$ grep apple fruitlist.txt</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1036


<p id="ch2intro_19d"></a>In this case, <span class="emphasis"><em>grep</em></span> prints all lines containing 'apple' from the file <span class="emphasis"><em>fruitlist.txt</em></span>, regardless of word boundaries; therefore lines containing 'pineapple' or 'apples' are also printed. The <span class="emphasis"><em>grep</em></span> command is case sensitive by default, so this example's output does not include lines containing 'Apple' (with a capital A) unless they also contain 'apple'.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1037


<p id="ch2intro_19e"></a>Like most Unix commands, <span class="emphasis"><em>grep</em></span> accepts command line arguments to change this and many other behaviors. For example:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1038


<pre class="programlisting">$ grep -i apple fruitlist.txt</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1039


<p id="ch2intro_19f"></a>This prints all lines containing 'apple' regardless of capitalization. The '-i' argument tells <span class="emphasis"><em>grep</em></span> to be case insensitive, or to ignore case.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1040


<p id="ch2intro_1a0"></a>To print all lines containing 'apple' as a word ('pineapple' and 'apples' will not match):</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1041


<pre class="programlisting">$ grep -w apple fruitlist.txt</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1042


<p id="ch2intro_1a1"></a>Regular expressions can be used to match more complicated queries.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1043


<div class="section" title="13.1.1.1. Variations">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1044


<div class="titlepage"><div><div><h5 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1045


<a name="id2987484"></a>13.1.1.1. Variations</h5></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1046


<p id="ch2intro_1a2"></a>There are countless implementations and derivatives of <span class="emphasis"><em>grep</em></span> available for many operating systems. Early variants of <span class="emphasis"><em>grep</em></span> included <span class="emphasis"><em>egrep</em></span> and <span class="emphasis"><em>fgrep</em></span>. The former applies an extended regular expression syntax that was added to Unix after Ken Thompson's original regular expression implementation. The latter searches for any of a list of 'fixed' strings using the Aho-Corasick algorithm. These variants are embodied in most modern <span class="emphasis"><em>grep</em></span> implementations as command-line switches (and standardized as -E and -F in POSIX). In such combined implementations, <span class="emphasis"><em>grep</em></span> may also behave differently depending on the name by which it is invoked, allowing <span class="emphasis"><em>fgrep</em></span>, <span class="emphasis"><em>egrep</em></span>, and <span class="emphasis"><em>grep</em></span> to be links to the same program.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1047


<p id="ch2intro_1a3"></a><span class="emphasis"><em>pcregrep</em></span> is an implementation of <span class="emphasis"><em>grep</em></span> that uses Perl regular expression syntax.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1048


<p id="ch2intro_1a4"></a>Other commands contain the word 'grep' to indicate that they search (usually for regular expression matches). The <span class="emphasis"><em>pgrep</em></span> utility, for instance, displays the processes whose names match a given regular expression.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1049


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1050


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1051


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1052


<div class="section" title="13.2. tr">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1053


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1054


<a name="id2987563"></a>13.2. tr</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1055


<p id="ch2intro_1a5"></a><span class="emphasis"><em>tr</em></span> (abbreviated from <span class="emphasis"><em>translate</em></span> or <span class="emphasis"><em>transliterate</em></span>) is a command in Unix-like operating systems.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1056


<p id="ch2intro_1a6"></a>When executed, the program reads from the standard input and writes to the standard output. It takes as parameters two sets of characters, and replaces occurrences of the characters in the first set with the corresponding elements from the other set. For example,</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1057


<pre class="programlisting">$ tr 'abcd' 'jkmn'</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1058


<p id="ch2intro_1a7"></a>maps 'a' to 'j', 'b' to 'k', 'c' to 'm', and 'd' to 'n'.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1059


<p id="ch2intro_1a8"></a>Sets of characters may be abbreviated by using character ranges. The previous example could be written:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1060


<pre class="programlisting">$ tr 'a-d' 'jkmn'</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1061


<p id="ch2intro_1a9"></a>In POSIX compliant versions of <span class="emphasis"><em>tr</em></span> the set represented by a character range depends on the locale's collating order, so it is safer to avoid character ranges in scripts that might be executed in a locale different from that in which they were written. Ranges can often be replaced with POSIX character sets such as [:alpha:].</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1062


<p id="ch2intro_1aa"></a>The <span class="emphasis"><em>-c</em></span> flag complements the first set of characters.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1063


<pre class="programlisting">$ tr -cd '[:alnum:]'</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1064


<p id="ch2intro_1ab"></a>therefore removes all non-alphanumeric characters.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1065


<p id="ch2intro_1ac"></a>The <span class="emphasis"><em>-s</em></span> flag causes tr to compress sequences of identical adjacent characters in its output to a single token. For example,</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1066


<pre class="programlisting">$ tr -s '\n' '\n'</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1067


<p id="ch2intro_1ad"></a>replaces sequences of one or more newline characters with a single newline.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1068


<p id="ch2intro_1ae"></a>The <span class="emphasis"><em>-d</em></span> flag causes tr to delete all tokens of the specified set of characters from its input. In this case, only a single character set argument is used. The following command removes carriage return characters, thereby converting a file in DOS/Windows format to one in Unix format.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1069


<pre class="programlisting">$ tr -d '\r'</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1070


<p id="ch2intro_1af"></a>Most versions of <span class="emphasis"><em>tr</em></span>, including GNU <span class="emphasis"><em>tr</em></span> and classic Unix <span class="emphasis"><em>tr</em></span>, operate on single byte characters and are not Unicode compliant. An exception is the Heirloom Toolchest implementation, which provides basic Unicode support.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1071


<p id="ch2intro_1b0"></a>Ruby and Perl also have an internal <span class="emphasis"><em>tr</em></span> operator, which operates analogously. Tcl's <span class="emphasis"><em>string map</em></span> command is more general in that it maps strings to strings while <span class="emphasis"><em>tr</em></span> maps characters to characters.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1072


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1073


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1074


<div class="section" title="14. Elementary Regex">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1075


<div class="titlepage"><div><div><h2 class="title" style="clear: both">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1076


<a name="id2987713"></a>14. Elementary Regex</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1077


<p id="ch2intro_1b1"></a>In computing, regular expressions provide a concise and flexible means for identifying strings of text of interest, such as particular characters, words, or patterns of characters. A regular expression (often shortened to regex or regexp) is written in a formal language that can be interpreted by a regular expression processor, a program that either serves as a parser generator or examines text and identifies parts that match the provided specification.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1078


<p id="ch2intro_1b2"></a>Regular expressions are used by many text editors, utilities, and programming languages to search and manipulate text based on patterns. For example, Perl, Ruby and Tcl have a powerful regular expression engine built directly into their syntax. Several utilities provided by Unix distributions—including the editor <span class="emphasis"><em>ed</em></span> and the filter <span class="emphasis"><em>grep</em></span> — were the first to popularize the concept of regular expressions.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1079


<p id="ch2intro_1b3"></a>Traditional Unix regular expression syntax followed common conventions but often differed from tool to tool. The IEEE POSIX <span class="emphasis"><em>Basic Regular Expressions</em></span> (BRE) standard (released alongside an alternative flavor called Extended Regular Expressions or ERE) was designed mostly for backward compatibility with the traditional (Simple Regular Expression) syntax but provided a common standard which has since been adopted as the default syntax of many Unix regular expression tools, though there is often some variation or additional features. Many such tools also provide support for ERE syntax with command line arguments.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1080


<p id="ch2intro_1b4"></a>In the BRE syntax, most characters are treated as literals — they match only themselves (i.e., a matches "a"). The exceptions, listed below, are called metacharacters or metasequences.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1081


<table summary="Elementary Regex" border="1"><colgroup>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1082


<col width="13">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1083


<col width="60">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1084


</colgroup></table>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1085


<div class="section" title="14.1. Lazy quantification">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1086


<div class="titlepage"><div><div><h3 class="title">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1087


<a name="id2988062"></a>14.1. Lazy quantification</h3></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1088


<p id="ch2intro_1c9"></a>The standard quantifiers in regular expressions are greedy, meaning they match as much as they can, only giving back as necessary to match the remainder of the regex. For example, someone new to regexes wishing to find the first instance of an item between &lt; and &gt; symbols in this example:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1089


<pre class="programlisting">Another whale explosion occurred on &lt;January 26&gt;, &lt;2004&gt;.</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1090


<p id="ch2intro_1ca"></a>...would likely come up with the pattern &lt;.*&gt;, or similar. However, this pattern will actually return "&lt;January 26&gt;, &lt;2004&gt;" instead of the "&lt;January 26&gt;" which might be expected, because the <span style="color: red">&lt;title_reference&gt;*&lt;/title_reference&gt;</span> quantifier is greedy — it will consume as many characters as possible from the input, and "January 26&gt;, &lt;2004" has more characters than "January 26".</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1091


<p id="ch2intro_1cb"></a>Though this problem can be avoided in a number of ways (e.g., by specifying the text that is not to be matched: &lt;[^&gt;]*&gt;), modern regular expression tools allow a quantifier to be specified as <span class="emphasis"><em>lazy</em></span> (also known as non-greedy, reluctant, minimal, or ungreedy) by putting a question mark after the quantifier (e.g., &lt;.*?&gt;), or by using a modifier which reverses the greediness of quantifiers (though changing the meaning of the standard quantifiers can be confusing). By using a lazy quantifier, the expression tries the minimal match first. Though in the previous example lazy matching is used to select one of many matching results, in some cases it can also be used to improve performance when greedy matching would require more backtracking.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1092


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1093


</div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1094


<div class="section" title="15. One Liners">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1095


<div class="titlepage"><div><div><h2 class="title" style="clear: both">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1096


<a name="id2988138"></a>15. One Liners</h2></div></div></div>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1097


<p id="ch2intro_1cc"></a>A <span class="emphasis"><em>one-liner</em></span> is textual input to the command-line of an operating system shell that performs some function in just one line of input.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1098


<p id="ch2intro_1cd"></a>The one liner can be</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1099


<span style="color: red">&lt;block_quote&gt;<div class="orderedlist"><ol class="orderedlist" type="1">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1100


<li class="listitem"><p id="ch2intro_1ce"></a>An expression written in the language of the shell.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1101


<li class="listitem"><p id="ch2intro_1cf"></a>The invocation of an interpreter together with program source for the interpreter to run.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1102


<li class="listitem"><p id="ch2intro_1d0"></a>The invocation of a compiler together with source to compile and













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1103


instructions for executing the compiled program.</p></li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1104


</ol></div>&lt;/block_quote&gt;</span><p id="ch2intro_1d1"></a>Certain dynamic scripting languages such as AWK, sed, and perl have traditionally been adept at expressing one-liners. Specialist shell interpreters such as these Unix shells or the Windows PowerShell, allow for the construction of powerful one-liners.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1105


<p id="ch2intro_1d2"></a>The use of the phrase one-liner has been widened to also include program-source for any language that does something useful in one line.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1106


<p id="ch2intro_1d3"></a>The word <span class="emphasis"><em>One-liner</em></span> has two references in the index of the book <span class="emphasis"><em>The AWK Programming Language</em></span> (the book is often referred to by the abbreviation TAPL). It explains the programming language AWK, which is part of the Unix operating system. The authors explain the birth of the One-liner paradigm with their daily work on early Unix machines:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1107


<pre class="programlisting">“The 1977 version had only a few built-in variables and predefined functions. It was designed for writing short programs [...] Our model was that an invocation would be one or two lines long, typed in and used immediately. Defaults were chosen to match this style [...] We, being the authors, knew how the language was supposed to be used, and so we only wrote one-liners.”</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1108


<p id="ch2intro_1d4"></a>Notice that this original definition of a One-liner implies immediate execution of the program without any compilation. So, in a strict sense, only source code for interpreted languages qualifies as a One-liner. But this strict understanding of a One-liner was broadened in 1985 when the IOCCC introduced the category of Best One Liner for C, which is a compiled language.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1109


<p id="ch2intro_1d5"></a>The TAPL book contains 20 examples of One-liners (A Handful of Useful awk One-Liners) at the end of the book's first chapter.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1110


<p id="ch2intro_1d6"></a>Here are the first few of them:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1111


<span style="color: red">&lt;block_quote&gt;<div class="orderedlist"><ol class="orderedlist" type="1">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1112


<li class="listitem">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1113


<p id="ch2intro_1d7"></a>Print the total number of input lines:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1114


<p id="ch2intro_1d8"></a>END { print NR }</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1115


</li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1116


<li class="listitem">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1117


<p id="ch2intro_1d9"></a>Print the tenth input line:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1118


<p id="ch2intro_1da"></a>NR == 10</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1119


</li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1120


<li class="listitem">













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1121


<p id="ch2intro_1db"></a>Print the last field of every input line:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1122


<p id="ch2intro_1dc"></a>{ print $NF }</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1123


</li>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1124


</ol></div>&lt;/block_quote&gt;</span><p id="ch2intro_1dd"></a>One-liners are also used to show off the differential expressive power of programming languages. Frequently, one-liners are used to demonstrate programming ability. Contests are often held to see who can create the most exceptional one-liner.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1125


<p id="ch2intro_1de"></a>The following example is a C program (a winning entry in the "Best one-liner" category of the IOCCC, here split to two lines for presentation).:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1126


<pre class="programlisting">main(int c,char**v){return!m(v[1],v[2]);}m(char*s,char*t){return













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1127


*t-42?*s?63==*t|*s==*t&amp;&amp;m(s+1,t+1):!*t:m(s,t+1)||*s&amp;&amp;m(s+1,t);}</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1128


<p id="ch2intro_1df"></a>This one-liner program is a <span class="emphasis"><em>glob pattern matcher</em></span>. It understands the glob characters '*' meaning 'zero or more characters' and '?' meaning exactly one character, just like most Unix shells.</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1129


<p id="ch2intro_1e0"></a>Run it with two args, the string and the glob pattern. The exit status is 0 (shell true) when the pattern matches, 1 otherwise. The glob pattern must match the whole string, so you may want to use * at the beginning and end of the pattern if you are looking for something in the middle. Examples:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1130


<pre class="programlisting">$ prog foo 'f??'; echo $?








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




  1131









1






672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1132


$ prog 'best short program' '??st*o**p?*'; echo $?</pre>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1133


<p id="ch2intro_1e1"></a>Here is a one line shell script to show directories:</p>













672eaaab9204
Added some new html files that failed earlier during change from rst



amit@thunder


parents: 
0

diff
changeset




  1134


<pre class="programlisting">$ ls -R | grep ":$" | sed -e 's/:$//' -e 's/[^-][^\/]*\//--/g' -e 's/^/   /' -e 's/-/|/'</pre>








0






8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




  1135


</div>













8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




  1136


</div>













8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




  1137


</div></body>













8083d21c0020
The first commit of all the required files for the review app



amit@thunder


parents: 

diff
changeset




  1138


</html>















SEES-hacks