gistfile1.txt

# Timeout based
lockfile=/var/run/script.lock
(
    flock --timeout 60 200 || ( echo "UNKNOWN: Lock failed"; exit 3)
    stuff;
 ) 200>${lockfile}

# Only allow one at a time
lockfile=/var/run/script.lock
if ( set -o noclobber; echo "$$" > "$lockfile") 2> /dev/null; 
then
    trap 'rm -f "$lockfile"; exit $?' INT TERM EXIT
    stuff;
    rm -f "$lockfile"
    trap - INT TERM EXIT
else
    echo "UNKNOWN: Failed to acquire lockfile: $lockfile. Held by $(cat $lockfile)"
    exit 3
fi