bash flock: exit if can't acquire lock
flock -n -e 200 || exit 1flock -n tells you it failed by returning a failure code (something other than zero). You could instead do set -e at the top of your script to make it exit when it sees any unchecked error.
Depending on your application, you might want to exit 0 to indicate success when the lock can't be acquired.
We use exclusive lock on the script file itself, $0 is the name of command file.
exec 200<$0flock -n 200 || exit 1The whole solution is in two lines of code. But the trick is to open $0 for reading and then obtain exclusive lock for it.