Bash For Loop

17. September 2020
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In scripting languages such as Bash, loops are very helpful for automating repetitive tasks.

There are three basic loop constructs in Bash scripting, "for loop", "while loop", "until loop".

In this post, I will cover the basics of "for loops" in Bash.

The goal is that transferring files from different hosts to the one destination.

The Standard Syntax for Loop

The for loop iterates over a list of items and performs the given set of commands.

for item in [LIST]
do
  [COMMANDS]
done

The list can be a series of strings separated by spaces, a range of numbers, output of a command, an array, and so on.

Loop Over Strings

Since, our goal is transferring files from different directories or even different host machine to one destination, we just need to consider the location of the files as list of strings and run this following code.

h1=/host1-adr/files
h2=/host2-adr/files
h3=/host3-adr/files
des=/the-adr-destination
for adr in $h1 $h2 $h3
do
 scr -r $adr/* $des
done

\ Your you can consider the different host locations as an array and use the for loop like this:

hosts=('/host1-adr/files' '/host2-adr/files' )
des=/the-adr-destination
for adr in "${hosts[@]}"
do
 scr -r $adr/* $des
done

It is so simple and fun, when you want to repeat so many commands that can be written by a nice for-loop with less code.

If you have any questions or feedback, feel free to leave a comment.

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