NAME
Lazy::Lockfile - File locking for the lazy.
SYNOPSIS
use Lazy::Lockfile;
my $lockfile = Lazy::Lockfile->new() || die "Couldn't get lock!";
...
# Lock is released when $lockfile goes out of scope or your program exits.DESCRIPTION
Lazy::Lockfile is a module designed for simple locking, requiring very little of the user. Once the object is instanced, the lock will be held as long as object is in scope. When the object is destroyed, the lock is released.
Lazy::Lockfile is smart enough to detect stale lockfiles from PIDs no longer on the system.
NOTES
Lazy::Lockfile is not safe for use on NFS volumes.
When not using the no_pid option, Lazy::Lockfile is unable to detect a process running as a user different than the current process (unless the current process is running as root). This is due to the way in which Lazy::Lockfile checks for a running process. In this scenario, it is recommended that users use the no_pid option.
USAGE
All of the magic in Lazy::Lockfile is done through the constructor and destructor.
METHODS
new
Constructor for Lazy::Lockfile.
Parameters
Accepts a single optional parameter, a hashref containing the following options:
location
Specifies the full path to the location of the lockfile. Defaults to:
'/tmp/' . (fileparse($0))[0] . '.pid'I.e., the name of the program being run, with a .pid extension, in /tmp/.
no_pid
If true, instead of writing the PID file, a value of "0" is written instead. When read by another instance of Lazy::Lockfile attempting to aquire the lock, no PID check will be performed and the lock will be assumed to be active as long as the file exists. Defaults to false.
delete_on_destroy
If true, sets the "delete on destroy" flag. This flag defaults to true, which causes the lockfile to be removed when the object is destroyed. Generally, this is the desired behavior. When set to false, this flag prevents the lockfile from being removed automatically when the object is destroyed. See also delete_on_destroy.
Compatibility
For compatability with older versions of Lazy::Lockfile (pre-1.0), a single optional parameter is accepted, the path to the lockfile. This parameter functions the same as the 'location' parameter described above.
Return value
If the lock can not be obtained, undef is returned (and $! will contain useful information). Otherwise, the lock is exclusive to this process, as long as the object exists.
name
Returns the file name of the lockfile.
delete_on_destroy
Gets or sets the "delete on destroy" flag.
If called without a parameter (or with undef), delete_on_destroy will return the current state of the "delete on destroy" flag. If called with a parameter, this flag will be set.
unlock
Explicitly removes the lockfile, just as if the object were destroyed. Once this has been called, delete_on_destroy will be set to false, since the lock has already been deleted. Once this method is called, there is not much use left for the object, so the user may as well delete it now.
unlock should be used when the lockfile needs to be removed deterministicly while the program is running. If you simply remove all references to the Lazy::Lockfile object, the lock will be freed when garbage collection is run, which is not guaranteed to happen until the program exits (though it will likely happen immediately).
CHANGES
2010-06-22, 1.16 - jeagle
Version bumps for migration to CPAN.
2009-12-03, 1.14 - jeagle
Fix a bug causing lockfiles with no_pid to not be deleted on destroy/unlink.
2009-12-03, 1.13 - jeagle
Add the unlock method, to allow for deterministic lockfile removal at runtime.
2009-11-30, 1.12 - jeagle
Update documentation to clarify delete_on_destroy parameter default setting.
2009-07-06, 1.11 - jeagle
Fix error thrown when running with taint checking enabled.
2009-07-06, 1.10 - jeagle
Fix a bug with lockfile location being overwritten with the default.
2009-07-06, 1.9 - jeagle
Add new parameter, no_pid, which disabled active lockfile checks.
Allow constructor to accept multiple parameters via hashref.
2009-06-10, 0.4 - jeagle
Introduce the delete_on_destroy flag.
2009-06-03, 0.3 - jeagle
Open pid file with O_NOFOLLOW, to avoid symlink attacks.
Change default pid file location from /var/tmp to /tmp.
Correct dates in CHANGES section.
Add useful error indicators, documentation on error detection.
2009-04-27, 0.2 - jeagle
Fix a bug with unspecified lockfile paths trying to create impossible file names.
2009-04-06, v0.1 - jeagle
Inital release.