CODEWITHSUNDEEP
bashshellbackgroundwaitjobs
teracow
teracow

Reputation: 229

BASH - After 'wait', why does 'jobs -p' sometimes show 'Done' for a background process?

The short version: My bash script has a function.

This function then launches several instances (a maximum of 10) of another function in the background (with &).

I keep a count of how many are still active with jobs -p | wc -w in a do loop. When I'm done with the loop, I break.

I then use wait to ensure that all those processes terminate before continuing.

However, when I check the count (with jobs -p) I sometimes find this: 

[10]   9311 Done                    my_background_function_name $param

How can I get wait to only proceed when all the launched child-processes have completely terminated and the jobs list is empty?

Why are jobs sometimes shown with "Done" and sometimes not?

Clearly, my knowledge of how jobs works is deficient. :)

Thanks.

Upvotes: 2

Views: 1580

Answers (1)

alvaro
alvaro

Reputation: 11

Inside a bash script, it seems that when all jobs has ended, jobs -p still returns the last one finished. This works for me in bash:

while true; do
  sleep 5
  jobs_running=($(jobs -l | grep Running | awk '{print $2}'))
  if [ ${#jobs_running[@]} -eq 0 ]; then
    break
  fi
  echo "Jobs running: ${jobs_running[@]}"
done

Using the "wait" command you cannot tell when each process ends. With the previous algorithm you can.

Upvotes: 1

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