Simple job control in bash
As part of our system test suite, I need to run a bunch of programs at the same time, and have them restart if they crash.
I also want them all to die at the same time if I stop the foreground process.
I can’t use
systemd, because these aren’t system processes; I’m running them locally (probably
from a Makefile). I also spent some time messing around with
forever, but I couldn’t persuade it to run non-node
Let’s use bash instead…
The plan here is to run a couple of netcat instances, listening on different ports. These will stand in for our real processes.
I’m going to run them without the
-k (keep listening) switch, because that gives me an easy way to make them exit (by sending them data).
We can send them data with
echo "Hello World!" > /dev/tcp/localhost/9220.
#!/bin/bash # When the script exits, kill the current process group. trap "kill -- -$BASHPID" EXIT # Run the command in the background. # If it stops, restart it. (while true; do nc -l 9220 done) & (while true; do nc -l 9221 done) & # Wait indefinitely (for Ctrl+C). cat
If you want a short delay before restarting the process…
(while true; do nc -l 9220 sleep 1 done) &
If you want the process to restart only if it exits with a non-zero status:
(unless nc -l 9220; do sleep 1 done) &