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<h1 class="SECT1"><a id="FILE-COMMANDS-OUTPUT" name="FILE-COMMANDS-OUTPUT">10.3 Simple
Output: <tt class="COMMAND">cat</tt> and <tt class="COMMAND">echo</tt></a></h1>
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<h2 class="SECT2"><a id="AEN3559" name="AEN3559">10.3.1 <tt
class="COMMAND">cat</tt></a></h2>
<p><tt class="COMMAND">cat</tt>(1) is short for “concatenate”. It was
originally designed to merge text files into one, but can be used for many other
purposes.</p>
<p>To merge two or more files into one, you simply list the files after the <tt
class="COMMAND">cat</tt> command and then redirect the new output to a file. <tt
class="COMMAND">cat</tt> works with standard input and standard output, so you have to
use the shell redirection characters. For example:</p>
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<samp class="PROMPT">%</samp> <kbd
class="USERINPUT">cat file1 file2 file3 > bigfile</kbd>
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<p>This command takes the contents of <tt class="FILENAME">file1</tt>, <tt
class="FILENAME">file2</tt>, and <tt class="FILENAME">file3</tt> and merges it all
together. The new output is sent to standard out.</p>
<p>One can also use <tt class="COMMAND">cat</tt> to display files. Many people <tt
class="COMMAND">cat</tt> text files through the <tt class="COMMAND">more</tt> or <tt
class="COMMAND">less</tt> commands, like this:</p>
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">cat file1 | more</kbd>
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<p>That will display the <tt class="FILENAME">file1</tt> file and pipe it through the <tt
class="COMMAND">more</tt> command so that you only get one screen at a time.</p>
<p>Another common use for <tt class="COMMAND">cat</tt> is copying files. You can copy any
file around with <tt class="COMMAND">cat</tt>, like this:</p>
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">cat /bin/bash > ~/mybash</kbd>
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<p>The <tt class="COMMAND">/bin/bash</tt> program is copied to your home directory and
named <tt class="FILENAME">mybash</tt>.</p>
<p><tt class="COMMAND">cat</tt> has many uses and the ones discussed here are just a few.
Since <tt class="COMMAND">cat</tt> makes extensive use of standard input and standard
output, it is ideal for use in shell scripts or part of other complex commands.</p>
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<h2 class="SECT2"><a id="AEN3603" name="AEN3603">10.3.2 <tt
class="COMMAND">echo</tt></a></h2>
<p>The <tt class="COMMAND">echo</tt>(1) command displays the specified text on the
screen. You specify the string to display after the <tt class="COMMAND">echo</tt>
command. By default <tt class="COMMAND">echo</tt> will display the string and print a
newline character after it. You can pass the <var class="OPTION">-n</var> option to
suppress the printing of the newline. The <var class="OPTION">-e</var> option will cause
<tt class="COMMAND">echo</tt> to search for escape characters in the string and execute
them.</p>
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