Make a variable containing all digits from the stdout of the command run directly before it

I am trying to make a bash shell script that launches some jobs on a queuing system. After a job is launched, the launch command prints the job-id to the stdout, which I would like to ‘trap’ and then use in the next command. The job-id digits are the only digits in the stdout message.

#!/bin/bash
./some_function
>>> this is some stdout text and the job number is 1234...

and then I would like to get to:

echo $job_id
>>> 1234

My current method is using a tee command to pipe the original command’s stdout to a tmp.txt file and then making the variable by grepping that file with a regex filter…something like:

echo 'pretend this is some dummy output from a function 1234' 2>&1 | tee tmp.txt
job_id=`cat tmp.txt | grep -o '[0-9]'`
echo $job_id

>>> pretend this is some dummy output from a function 1234
>>> 1 2 3 4

…but I get the feeling this is not really the most elegant or ‘standard’ way of doing this. What is the better way to do this?

And for bonus points, how do I remove the spaces from the grep+regex output?

Answer

You can use grep -o when you call your script:

jobid=$(echo 'pretend this is some dummy output from a function 1234' 2>&1 | 
    tee tmp.txt | grep -Eo '[0-9]+$')

echo "$jobid"
1234

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Answer