| #! /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. |
