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- #! /bin/sh
- # Shell-based mutex using mkdir.
- lockdir="$1" prog="$2"; shift 2 || exit 1
- # Remember when we started trying to acquire the lock.
- count=0
- touch lock-stamp.$$
- trap 'rm -r "$lockdir" lock-stamp.$$' 0
- until mkdir "$lockdir" 2>/dev/null; do
- # Say something periodically so the user knows what's up.
- if [ `expr $count % 30` = 0 ]; then
- # Reset if the lock has been renewed.
- if [ -n "`find \"$lockdir\" -newer lock-stamp.$$`" ]; then
- touch lock-stamp.$$
- count=1
- # Steal the lock after 5 minutes.
- elif [ $count = 300 ]; then
- echo removing stale $lockdir >&2
- rm -r "$lockdir"
- else
- echo waiting to acquire $lockdir >&2
- fi
- fi
- sleep 1
- count=`expr $count + 1`
- done
- echo $prog "$@"
- $prog "$@"
- # The trap runs on exit.
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