Here is the video version, if you prefer it:
for loops are used for iterating. Iterating means going over a sequence of values.
Here is an example of a for loop, modeled after (“Bash For Loop Examples,” n.d.).
#!/bin/bash
for i in 1 2 3 4 5
do
echo $i
done
This will produce the following output:
mislav@mislavovo-racunalo:~/Linux_folder$ ./tutorialScript.sh
1
2
3
4
5
What just happened? The variable i first took on the value of 1 (the first element in the sequence). Then it echoed its value. Then variable i took the next value in the sequence (the value after the value it currently had). So i was 2. Then 2 got outputted – and so on until the end of the sequence.
You can specify numerical sequences more easily (the above one could have been written as {1..5}) and you can iterate over other sequences (not just numbers, but other things – files for example). I leave you to consult the reference and Google for some further examples.
Hope you learned something useful!
References
Bash For Loop Examples. (n.d.). Retrieved February 22, 2020, from https://www.cyberciti.biz/faq/bash-for-loop/