multi-flock-example.sh

#!/bin/bash

# bash multi flock
#
# allow 3 instances of a bash function running at the same time

run_instance() {
    (
        flock -n 99 || return 1
        echo "starting instance $@..."
        # do something here
        sleep 10
        echo "done"
    ) 99>/tmp/test-${@}.lock
}

run_instance 1 || run_instance 2 || run_instance 3 || echo "BLOCKED!"