Use PID of child process in bash

Launch a child process, get its PID, show a message, wait for the child to complete and show another message:

  • ls -R /var >> /dev/null &  echo PID $! running; wait $!; echo PID $! completed


  1. Use of & after the command is mandatory, or else you will not get the PID you want.
  2. Using asynchronous execution in combination with wait command is, obviously, equivalent to using a synchronous call, except that it gives you more power.
  3. Using wait with no arguments will make the parent process to wait for all children it ever spawned, using wait with a PID will make it wait only for that particular process.




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