shell programming - locking

lockfile=/var/lock/proc$$.lock if ( set -o noclobber; echo "$$" > ${lockfile} ) 2> /dev/null; then trap 'rm -f ${lockfile}; exit $?' INT TERM EXIT # do stuff here # clean up and release your trap rm -f ${lockfile} trap - INT TERM EXIT else printf "lock exists: %s owned by process %s" ${lockfile} $(cat ${lockfile}) fi

lockfile=/var/lock/proc-whatever.lock tmpfile=${lockfile}.tmp echo $$ > ${tmpfile} if ln ${tmpfile} ${lockfile} 2>&-; then printf "locked" else printf "locked by %s" $(<${lockfile}) rm ${tmpfile} exit fi trap "rm ${tmpfile} ${lockfile}" 0 1 2 3 15 # do what you need to