# phpman > perldoc > Mail::Box::Locker::Flock

## NAME
    [Mail::Box::Locker::Flock](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker%3A%3AFlock/markdown) - lock a folder using kernel file-locking

## INHERITANCE
     [Mail::Box::Locker::Flock](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker%3A%3AFlock/markdown)
       is a [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)
       is a [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

## SYNOPSIS
     See [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

## DESCRIPTION
    The "::Flock" object locks the folder by creating an exclusive lock on the file using the
    kernel's "flock" facilities. This lock is created on a separate file-handle to the folder file,
    so not the handle which is reading.

    File locking does not work in some situations, for instance for operating systems do not support
    "flock".

    Extends "DESCRIPTION" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

## METHODS
    Extends "METHODS" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

### Constructors
    Extends "Constructors" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

    [Mail::Box::Locker::Flock](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker%3A%3AFlock/markdown)->new(%options)
         -Option --Defined in       --Default
          expires  [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)  1 hour
          file     [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)  undef
          folder   [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)  <undef>
          log      [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)     'WARNINGS'
          method   [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)  'FLOCK'
          timeout  [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)  10
          trace    [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)     'WARNINGS'

        expires => SECONDS
        file => FILENAME
        folder => FOLDER
        log => LEVEL
        method => STRING|CLASS|ARRAY
        timeout => SECONDS|'NOTIMEOUT'
        trace => LEVEL

### Attributes
    Extends "Attributes" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

    $obj->expires( [SECONDS] )
        Inherited, see "Attributes" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

    $obj->timeout( [SECONDS] )
        Inherited, see "Attributes" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

### The Locker
    Extends "The Locker" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

    $obj->filename( [$filename] )
        Inherited, see "The Locker" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

    $obj->folder( [$folder] )
        Inherited, see "The Locker" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

    $obj->name()
        Inherited, see "The Locker" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

### Locking
    Extends "Locking" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

    $obj->hasLock()
        Inherited, see "Locking" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

    $obj->isLocked()
    $obj->lock()
    $obj->unlock()
        Inherited, see "Locking" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

### Error handling
    Extends "Error handling" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

    $obj->AUTOLOAD()
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->addReport($object)
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
    [Mail::Box::Locker::Flock](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker%3A%3AFlock/markdown)->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->errors()
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->log( [$level, [$strings]] )
    [Mail::Box::Locker::Flock](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker%3A%3AFlock/markdown)->log( [$level, [$strings]] )
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->logPriority($level)
    [Mail::Box::Locker::Flock](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker%3A%3AFlock/markdown)->logPriority($level)
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->logSettings()
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->notImplemented()
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->report( [$level] )
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->reportAll( [$level] )
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->trace( [$level] )
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

    $obj->warnings()
        Inherited, see "Error handling" in [Mail::Reporter](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3AReporter/markdown)

### Cleanup
    Extends "Cleanup" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown).

    $obj->DESTROY()
        Inherited, see "Cleanup" in [Mail::Box::Locker](https://www.chedong.com/phpMan.php/perldoc/Mail%3A%3ABox%3A%3ALocker/markdown)

## DIAGNOSTICS
    Warning: Folder $folder already flocked
        The folder is already locked, but you attempt to lock it again. The behavior of double
        flock's is platform dependent, and therefore should not be attempted. The second lock is
        ignored (but the unlock isn't)

    Error: Package $package does not implement $method.
        Fatal error: the specific package (or one of its superclasses) does not implement this
        method where it should. This message means that some other related classes do implement this
        method however the class at hand does not. Probably you should investigate this and probably
        inform the author of the package.

    Error: Unable to check lock file $filename for $folder: $!
        To check whether the filename is used to flock a folder, the file must be opened. Apparently
        this fails, which does not mean that the folder is locked neither that it is unlocked.

    Error: Unable to open flock file $filename for $folder: $!
        For flock-ing a folder it must be opened, which does not succeed for the specified reason.

    Error: Will never get a flock at $filename for $folder: $!
        Tried to flock the folder, but it did not succeed. The error code received from the OS
        indicates that it will not succeed ever, so we do not need to try again.

## SEE ALSO
    This module is part of Mail-Box distribution version 3.009, built on August 18, 2020. Website:
    <http://perl.overmeer.net/CPAN/>

## LICENSE
    Copyrights 2001-2020 by [Mark Overmeer]. For other contributors see ChangeLog.

    This program is free software; you can redistribute it and/or modify it under the same terms as
    Perl itself. See <http://dev.perl.org/licenses/>