Something

# MUTEXecho -n ">>> Locking: " >&2if mkdir "${LOCKDIR}"; then    # lock succeeded    echo "$$" >"${PIDFILE}"    trap 'rm -rf "${LOCKDIR}"' 0    trap trap 'exit ${ENO_RECVSIG}' 1 2 3 15    echo "success, installed signal handlers"else    # lock failed    OTHERPID="$(cat "${PIDFILE}")"    echo "lock failed, PID ${OTHERPID} is active" >&2    exit ${ENO_LOCKFAIL}fi# /MUTEX