---
layout: page
category_title: interm
category-page: interm
tags: tee shell command
author: Nicola Brunner
title: tee
---

<p>The <code>tee</code> command is used to split the output of a program, doing
this the output can be displayed in the shell and in the same time written in a
file. This is useful, for example, if we want to capture intermediate outputs of
a long program.
The command is named after the T-splitter used in plumbing, because they have
similar functions.</p>
<br>

<h3>Usage:</h3>
<p>The default tee command syntax is:</p>

<pre>tee [flags] [file]</pre>

<p>Where <code>[flags]</code> are the tee flags (below you will find more info),
and argument <code>[file]</code> is a file or a list of files, each of which
receives the output.</p>
<br>

<h3>Flags:</h3>

<p>The most common flags of tee are:</p>
<ul>
  <li><code>-a</code> Appends the output to each file, rather than overwriting it.</li>
  <li><code>-i</code> Ignores interrupt signals.</li>
</ul>
<br>

<h3>Example:</h3>

<pre>date | tee example.txt</pre>

<p>Basically, with this example, we can see that tee writes the date in
example.txt, but shows also the output (in this case the date) in the shell.
If you wouldn’t your file be overwritten every time you use this command,
you should use <code>-a</code> that appends the output to the file.</p>