blog.oremj.com

Simple bash locking

I often need to create lock files in my scripts, so crontab doesn’t spawn more than one process.  This is a simple bash lock file function I like to use:

function create_lock {
        LOCK_NAME=$1
        if [[ -e "$LOCK_NAME" ]]
        then
                OLDPID=`cat $LOCK_NAME`
                if ps p $OLDPID > /dev/null
                then
                        return 1
                fi
                rm $LOCK_NAME
        fi
        echo $$ > $LOCK_NAME
        return 0
}

create_lock doesn’t handle race conditions, but it is typically good enough for me.