CODEWITHSUNDEEP
bash
bashprofile84
bashprofile84

Reputation: 99

How to run a command on each line of a multi line string variable in bash?

The variable $type is a multi line string variable containing:

car
plane

You can get the output above issuing echo "$type".

And I have a some_command that uses $type as one of its parameters.

In bash, how would you execute some_command so that it runs with each line of $type one after another? i.e. first some_command would run using car and then it would run again using plane and then the loop would stop once the line was empty i.e. no values left to execute some_command with.

Upvotes: 1

Views: 2737

Answers (2)

axiac
axiac

Reputation: 72226

The easiest way (in my opinion) is to use xargs with argument -L (limit):

echo "$type" | xargs -L 1 some_command

xargs takes each input line and passed the value as an argument to some_command.

some_command may have other arguments too. xargs adds the input line at the end of its arguments list and executes it.

On macOS it can be told to insert the input line into a different position by using -J but this is a non-standard FreeBSD extension that is not available in the GNU version of xargs (the version usually present on the Linux systems.)

Upvotes: 1

Pierre François
Pierre François

Reputation: 6061

Supposing the lines in $type do not contain white spaces other than the new line chars, try:

for line in $type; do echo working on "$line"; some_command "$line"; done

It is important not to surround the first occurence of $type with double quotes in the for statement, otherwise you will get all the lines at once.

Upvotes: 0

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