theshell.ch/site/pages/scripts/for-loop.html

---
layout: page
category-page: scripts
category-title: Scripting
tags: loop for done script scripting
author: Matteo Omenetti
title: For Loop
---

<!-- Introduction -->
The second type of loops are for loops.
They follow this syntax:
{% highlight bash %}
  for [variable] in [list] do
    [code]
  done
{% endhighlight %}

Their purpose is to <i>iterate</i> over a list. Also, while loops could do this,
you might argue... <br>
Of course, they could, but for loops are specifically meant to do this. Therefore, for instance,
you don't have to declare your counter variable outside the loop. Most importantly,
this variable can be accessed from inside the loop. <br>

For loops take this form:
{% highlight bash %}
for VARIABLE in 1 2 3 4 5 .. N
do
	command1
	command2
	commandN
done
{% endhighlight %}
<!-- End of Introduction -->

<!-- First Example -->
Here is a simple example:
{% highlight bash %}
for i in 1 2 3 4 5
do
   echo "Welcome $i times"
done
{% endhighlight %}

This first example of code simply displays a welcome message 5 times.
The output of this piece of code is:
<pre>
    Welcome 1 times
    Welcome 2 times
    Welcome 3 times
    Welcome 4 times
    Welcome 5 times
</pre>
<!-- End of First Example -->

<!-- Explanation of Numerical Range -->
There are also other ways to specify the <i> numerical range </i>. For instance, if
your numerical range is too big, you can simply write: <code> {1..100} </code>. This piece
of code means every natural number between 1 and 100 (both included). <br>
Ranges can also count backward like this: <code>{10..1}</code>.
You can even increment the numerical value by step of two: <code> {0..10..2} </code>.
This piece of code means every natural number between 0 and 10 with a step of two,
0 2 4 6... 10.
<!-- End of Explanation of Numerical Range -->