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2006-05-25T21:58:00Z

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{{lowercase|title=comm}}

'''<tt>comm</tt>''' is a [[:Category:Linux Command Line Tools|command line tool]] that is used to compare two files. It shows common lines in one column and differing lines in separate columns for left and right files. This functionally is similar to <tt>[[Diff (command)|diff]]</tt>.

One notable difference between <tt>comm</tt> and <tt>diff</tt> is that <tt>comm</tt> will not try to indicate that a line has "changed" between the two files; lines are either shown in the "from file #1", "from file #2", or "in both" columns. This feature can be especially useful when you wish two lines to be considered different even if they only have subtle differences.

== Example usage ==
Let's say you have two files, <tt>foo</tt> and <tt>bar</tt>, and you would like to know what is unique or the same in these two files.

* The <tt>foo</tt> file has the following lines:
<pre>
pears
mellons
</pre>

* The <tt>bar</tt> file has the following lines:
<pre>
apples
oranges
pears
</pre>

To find what lines are common in both of these files, type the following:
<pre>comm -12 foo bar</pre>
which will produce:
<pre>pears</pre>

To find what lines are unique to <tt>foo</tt>, type the following:
<pre>comm -23 foo bar</pre>
which will produce:
<pre>mellons</pre>

== See also ==
*[[Diff (command)|diff]]

==External links==
*[http://www.linuxmanpages.com/man1/comm.1.php] The programme's manpage

[[Category:Linux Command Line Tools]]

Comm (command) - Revision history

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