theshell.ch/site/pages/cmd/advanced/comm.html

---
layout: page
author: Domenico Votta
category-page: advanced
category-title: Advanced commands
tags: compare sorted files
title: comm
---
The <code>comm</code> is a command that compares two sorted files
line by line and writes the output: the lines that are in common and the lines that are unique.<br>

Here we have two files named <code>example1.txt</code> and
<code>example2.txt</code> that contain 5 elements, to test this command:<br>

<code>example1.txt</code>
{% highlight bash linenos %}
Icecream
Chocolate
Cake
Candy
Biscuit
{% endhighlight %}

<code>example2.txt</code>
{% highlight bash linenos %}
Bread
Chocolate
Tomato
Candy
Pizza
{% endhighlight %}

The syntax command is:
<pre>
comm [flag][file1] [file2]
</pre>

<pre>
comm example1.txt example2.txt
    Icecream
        Chocolate
    Cake
      Tomato
        Candy
    Biscuit
      Pizza
</pre>

<ul>
    <li>The elements of the first file have less indentation.</li>
    <li>The elements of the second file have some more indentation.</li>
    <li>The elements in common have even more indentation than those of the second file.</li>
</ul>

<h3>Flags</h3>

<ul>
  <li> <b>-1</b>: supress column 1</li>
  <li> <b>-2</b>: supress column 2</li>
  <li> <b>-3</b>: supress column 3</li>
</ul>