/lockable_script_boilerplate.sh
Forked from przemoc/lockable_script_boilerplate.sh
Last active Aug 29, 2015
#!/bin/bash | |
## Copyright (C) 2009 Przemyslaw Pawelczyk <przemoc@gmail.com> | |
## License: GNU General Public License v2, v3 | |
# | |
# Lockable script boilerplate | |
### HEADER ### | |
LOCKFILE="/var/lock/`basename $0`" | |
LOCKFD=99 | |
# PRIVATE | |
_lock() { flock -$1 $LOCKFD; } | |
_no_more_locking() { _lock u; _lock xn && rm -f $LOCKFILE; } | |
_prepare_locking() { eval "exec $LOCKFD>\"$LOCKFILE\""; trap _no_more_locking EXIT; } | |
# ON START | |
_prepare_locking | |
# PUBLIC | |
exlock_now() { _lock xn; } # obtain an exclusive lock immediately or fail | |
exlock() { _lock x; } # obtain an exclusive lock | |
shlock() { _lock s; } # obtain a shared lock | |
unlock() { _lock u; } # drop a lock | |
### BEGIN OF SCRIPT ### | |
# Simplest example is avoiding running multiple instances of script. | |
exlock_now || exit 1 | |
# Remember! Lock file is removed when one of the scripts exits and it is | |
# the only script holding the lock or lock is not acquired at all. |
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