NAME¶
INN::Utils::Shlock - Wrapper around the shlock program
DESCRIPTION¶
This Perl module wraps the
shlock(1) program so that it can easily be
used. Calling
shlock is more portable than using
flock(2) and
its corresponding Perl function because this function does not work as
expected on all existing systems.
See the
shlock(1) documentation for more information.
Using INN::Utils::Shlock is straight-forward:
use lib '<pathnews>/lib/perl';
use INN::Utils::Shlock;
my $lockfile = "myprogram.LOCK";
# Acquire a lock.
INN::Utils::Shlock::lock($lockfile);
# Do whatever you want. The lock prevents concurrent accesses.
# Unlock.
INN::Utils::Shlock::unlock($lockfile);
These two functions return 1 on success, 0 on failure. For example, the success
of (un)locking can be checked as:
INN::Utils::Shlock::lock($lockfile) or die "cannot create lock file";
or:
if (! INN::Utils::Shlock::lock($lockfile, 4)) {
die "giving up after 4 unsuccessful attempts to create lock file";
}
Instead of calling "unlock(
lockfile)", the
"releaselocks()" function can be called. It removes any leftover
locks, which is useful when several different locks are used. Another possible
use is to call it in an END code block:
END {
# In case we bail out, while holding a lock.
INN::Utils::Shlock::releaselocks();
}
INTERFACE¶
- lock(lockfile)
- Tries to create a lock file named lockfile.
This function returns 1 on success, 0 on failure.
- lock(lockfile, tries)
- Tries to create a lock file named lockfile. If it
fails, locking attempts are repeated once every 2 seconds for at most
tries times (including the first unsuccessful attempt).
This function returns 1 on success, 0 on failure.
- lock(lockfile, tries, delay)
- Tries to create a lock file named lockfile. If it
fails, locking attempts are repeated once every delay seconds for
at most tries times (including the first unsuccessful attempt).
Note that "lock( lockfile)" is equivalent to
"lock(lockfile, 1, 2)".
This function returns 1 on success, 0 on failure.
- releaselocks()
- Removes all the lock files previously created by calling
the "lock( lockfile)" function.
This function returns the number of removed lock files.
- unlock(lockfile)
- Removes the file named lockfile.
This function returns 1 on success, 0 on failure.
HISTORY¶
Documentation written by Julien Elie for InterNetNews.
$Id: Shlock.pm.in 9409 2012-05-28 18:43:20Z iulius $
SEE ALSO¶
perl(1),
shlock(1).