plucky (3) INN::Utils::Shlock.3pm.gz

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 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.

SEE ALSO

       perl(1), shlock(1).