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148 lines
5.5 KiB
HTML
148 lines
5.5 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta name="generator" content="HTML Tidy, see www.w3.org" />
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<title>Simple Output: cat and echo</title>
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<meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" />
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<link rel="HOME" title="Slackware Linux Essentials" href="index.html" />
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<link rel="UP" title="Handling Files and Directories" href="file-commands.html" />
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<link rel="PREVIOUS" title="Pagers: more, less, and most"
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href="file-commands-pagers.html" />
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<link rel="NEXT" title="Creation: touch and mkdir" href="file-commands-creation.html" />
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<link rel="STYLESHEET" type="text/css" href="docbook.css" />
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
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</head>
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<body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084"
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alink="#0000FF">
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<div class="NAVHEADER">
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<table summary="Header navigation table" width="100%" border="0" cellpadding="0"
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cellspacing="0">
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<tr>
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<th colspan="3" align="center">Slackware Linux Essentials</th>
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</tr>
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<tr>
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<td width="10%" align="left" valign="bottom"><a href="file-commands-pagers.html"
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accesskey="P">Prev</a></td>
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<td width="80%" align="center" valign="bottom">Chapter 10 Handling Files and
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Directories</td>
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<td width="10%" align="right" valign="bottom"><a href="file-commands-creation.html"
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accesskey="N">Next</a></td>
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</tr>
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</table>
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<hr align="LEFT" width="100%" />
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</div>
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<div class="SECT1">
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<h1 class="SECT1"><a id="FILE-COMMANDS-OUTPUT" name="FILE-COMMANDS-OUTPUT">10.3 Simple
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Output: <tt class="COMMAND">cat</tt> and <tt class="COMMAND">echo</tt></a></h1>
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<div class="SECT2">
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<h2 class="SECT2"><a id="AEN3559" name="AEN3559">10.3.1 <tt
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class="COMMAND">cat</tt></a></h2>
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<p><tt class="COMMAND">cat</tt>(1) is short for “concatenate”. It was
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originally designed to merge text files into one, but can be used for many other
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purposes.</p>
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<p>To merge two or more files into one, you simply list the files after the <tt
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class="COMMAND">cat</tt> command and then redirect the new output to a file. <tt
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class="COMMAND">cat</tt> works with standard input and standard output, so you have to
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use the shell redirection characters. For example:</p>
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<table border="0" bgcolor="#E0E0E0" width="100%">
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<tr>
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<td>
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<pre class="SCREEN">
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<samp class="PROMPT">%</samp> <kbd
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class="USERINPUT">cat file1 file2 file3 > bigfile</kbd>
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</pre>
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</td>
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</tr>
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</table>
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<p>This command takes the contents of <tt class="FILENAME">file1</tt>, <tt
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class="FILENAME">file2</tt>, and <tt class="FILENAME">file3</tt> and merges it all
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together. The new output is sent to standard out.</p>
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<p>One can also use <tt class="COMMAND">cat</tt> to display files. Many people <tt
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class="COMMAND">cat</tt> text files through the <tt class="COMMAND">more</tt> or <tt
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class="COMMAND">less</tt> commands, like this:</p>
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<table border="0" bgcolor="#E0E0E0" width="100%">
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<tr>
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<td>
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<pre class="SCREEN">
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">cat file1 | more</kbd>
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</pre>
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</td>
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</tr>
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</table>
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<p>That will display the <tt class="FILENAME">file1</tt> file and pipe it through the <tt
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class="COMMAND">more</tt> command so that you only get one screen at a time.</p>
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<p>Another common use for <tt class="COMMAND">cat</tt> is copying files. You can copy any
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file around with <tt class="COMMAND">cat</tt>, like this:</p>
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<table border="0" bgcolor="#E0E0E0" width="100%">
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<tr>
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<td>
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<pre class="SCREEN">
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">cat /bin/bash > ~/mybash</kbd>
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</pre>
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</td>
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</tr>
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</table>
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<p>The <tt class="COMMAND">/bin/bash</tt> program is copied to your home directory and
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named <tt class="FILENAME">mybash</tt>.</p>
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<p><tt class="COMMAND">cat</tt> has many uses and the ones discussed here are just a few.
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Since <tt class="COMMAND">cat</tt> makes extensive use of standard input and standard
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output, it is ideal for use in shell scripts or part of other complex commands.</p>
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</div>
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<div class="SECT2">
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<h2 class="SECT2"><a id="AEN3603" name="AEN3603">10.3.2 <tt
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class="COMMAND">echo</tt></a></h2>
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<p>The <tt class="COMMAND">echo</tt>(1) command displays the specified text on the
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screen. You specify the string to display after the <tt class="COMMAND">echo</tt>
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command. By default <tt class="COMMAND">echo</tt> will display the string and print a
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newline character after it. You can pass the <var class="OPTION">-n</var> option to
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suppress the printing of the newline. The <var class="OPTION">-e</var> option will cause
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<tt class="COMMAND">echo</tt> to search for escape characters in the string and execute
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them.</p>
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</div>
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</div>
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<div class="NAVFOOTER">
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<hr align="LEFT" width="100%" />
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<table summary="Footer navigation table" width="100%" border="0" cellpadding="0"
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cellspacing="0">
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<tr>
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<td width="33%" align="left" valign="top"><a href="file-commands-pagers.html"
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accesskey="P">Prev</a></td>
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<td width="34%" align="center" valign="top"><a href="index.html"
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accesskey="H">Home</a></td>
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<td width="33%" align="right" valign="top"><a href="file-commands-creation.html"
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accesskey="N">Next</a></td>
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</tr>
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<tr>
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<td width="33%" align="left" valign="top">Pagers: <tt class="COMMAND">more</tt>, <tt
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class="COMMAND">less</tt>, and <tt class="COMMAND">most</tt></td>
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<td width="34%" align="center" valign="top"><a href="file-commands.html"
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accesskey="U">Up</a></td>
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<td width="33%" align="right" valign="top">Creation: <tt class="COMMAND">touch</tt> and
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<tt class="COMMAND">mkdir</tt></td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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