#!/bin/sh
# filelock - A flexible file locking mechanism.
retries="10" # default number of retries
action="lock" # default action
nullcmd="/bin/true" # null command for lockfile
while getopts "lur:" opt; do
case $opt in
l ) action="lock" ;;
u ) action="unlock" ;;
r ) retries="$OPTARG" ;;
esac
done
shift $(($OPTIND - 1))
if [ $# -eq 0 ] ; then
cat << EOF >&2
Usage: $0 [-l|-u] [-r retries] lockfilename
Where -l requests a lock (the default), -u requests an unlock, -r X
specifies a maximum number of retries before it fails (default = $retries).
EOF
exit 1
fi
# Ascertain whether we have lockf or lockfile system apps
if [ -z "$(which lockfile | grep -v ''^no '')" ] ; then
echo "$0 failed: ''lockfile'' utility not found in PATH." >&2
exit 1
fi
if [ "$action" = "lock" ] ; then
if ! lockfile -1 -r $retries "$1" 2> /dev/null; then
echo "$0: Failed: Couldn''t create lockfile in time" >&2
exit 1
fi
else # action = unlock
if [ ! -f "$1" ] ; then
echo "$0: Warning: lockfile $1 doesn''t exist to unlock" >&2
exit 1
fi
rm -f "$1"
fi
exit 0
