The for loop

The for loop is one of the used structures when it comes to a Bash script and enables us to repeat one of more actions on each single item in a list. Its basic structure can be outlined as follows:

for placeholder in list_of_items
do
  action_1 $placeholder
  action_2 $placeholder
  action_n $placeholderdone

So, we use a placeholder, which will take at each round of the loop one of the values in the list of items, which will then be processed in the do section. Once all the list is scanned through, the loop is done, and we exit it. Let's start with a simple and nice example:

#!/bin/bash
for i in 1 2 3 4 5
do
  echo "$i"done

And now let's execute it:

zarrelli:~$ ./counter-simple.sh 
1
2
3
4
5

Actually, quite straightforward, but notice that the list can be the result of any kind of operations:

#!/bin/bash
for i in {10..1..2}
do
  echo "$i"done

In this case, we used a brace expansion to get a countdown with a step of 2:

zarrelli:~$ ./counter-brace.sh 
10
8
6
4
2

We can have a for loop...