---
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>

<p>The elements of the first file doesn't have the tab.</p>
<p>The elements of the second file have one tab.</p>
<p>The elements in common have two tabs.</p>

<h2>Flags</h2>

<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>