Question

I have a perl script runs in cron and if the script fails to run it leaves behind a lock file to prevent the script to run again.

I’m trying to run a bash script that checks if the process is running and checks to see if a lock file is left behind

if processes is running and lock file exists
exit 0;

if process is not running and lock file exists
rm lockfile.
exit 0;

if process does not exist and lock file is ‘not present’
exit 0;

I’ve been checking if the process exists running
ps ax |grep -v grep |grep process.pl

I’m looking for the conditionals in bash that I should be running here.

Thanks

Answer 1

The process.pl should write its process id into the lockfile, wihch is a common pattern. Then you can write the following code:

if [ -f "$lockfile" ]; then
  pid=$(cat "$lockfile")
  if kill -0 "$pid"; then
    : "running normally"
  else
    : "terminated somehow"
    rm -f "$lockfile"
  fi
fi