CODEWITHSUNDEEP
bashfor-loopwhile-loop
crysis405
crysis405

Reputation: 1131

Bash forked for loop with while loop control

I have a for loop that will cycle through all the files in a directory. I want to run a process on each file (in this example echo file name and sleep 5). However I want to be able to run this 5 files at a time (in the background with &). The problem is I can't figure out how to iterate $f within the while loop so that I don't end up processing the same file five times instead of five different files at the same time. 

#!/bin/bash

maxjobs=5

for f in `ls /home/user/`
do
 jobsrunning=0
  while [ $jobsrunning -lt $maxjobs ]
  do
    echo "Converting file"$f 
    sleep 5 & #wait for 5 seconds 
    jobsrunning=$((jobsrunning + 1))
    echo $jobsrunning
  done
wait
done

Upvotes: 1

Views: 80

Answers (1)

kojiro
kojiro

Reputation: 77079

You really just need to reset jobsrunning, and I don't think you need the inner loop at all. It's just a condition.

#!/bin/bash

maxjobs=5
jobsrunning=0
for f in /home/user/*; do
    if (( jobsrunning >= maxjobs )); then
        wait
        jobsrunning=0
    fi
    echo "converting"
    sleep 5 & # wait for how many seconds?
    (( jobsrunning++ ))
    echo "$jobsrunning"
done
wait

That said, this sounds like a job for parallel.

Upvotes: 3

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