prevent a jffs script to be run twice in parallel

[slytho]

Hi!

When I power on/reboot my AC86-router, it runs the '/jffs/scripts/wan0-connected' script twice. I can also see the wifi appear, then disappear after a few seconds and come back again after a few more seconds.

This causes the commands in the above said script to be run twice and in parallel.

My question: how can I prevent a bash script from being run twice and simultaneously when there's already another instance of the script running?

 

[slytho]

I think I found a solution working for reduced busybox command set:

# ensure script only runs exclusively, additional invocations return immediately
# https://linuxaria.com/howto/linux-shell-introduction-to-flock
scriptname=$(basename $0)
lock="/var/run/${scriptname}"
exec 200>$lock
flock -n 200 || { logger -t $0 -p user.err "Error: Another copy of $0 is running. Exiting" ; exit 1; }