---
name: "Mail::Box::Locker::POSIX"
section: "3pm"
platform: "linux"
package: "perl-mail-box"
version: "4.02-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Mail::Box::Locker::POSIX"
---

# Mail::Box::Locker::POSIX(3pm)

lock a folder using kernel file-locking

## NAME

Mail::Box::Locker::POSIX - lock a folder using kernel file-locking

## INHERITANCE

```
 Mail::Box::Locker::POSIX
   is a Mail::Box::Locker
   is a Mail::Reporter
```

## SYNOPSIS

```
  See Mail::Box::Locker
```

## DESCRIPTION

This locker object is created by the folder to get an exclusive lock on the file which contains the data using the kernel's POSIX facilities.  This lock is created on a separate file-handle to the folder file, so not the handle which is reading.

**WARNING**: Not all platforms support POSIX locking (via fcntl) and not always in the same way.  This implementation does not use XS to access the structure of **fcntl()**: it is better to use the ::FcntlLock which does. No, this implementation "guesses" the location of the bytes.

Extends "DESCRIPTION" in Mail::Box::Locker.

## METHODS

Extends "METHODS" in Mail::Box::Locker.

### Constructors

Extends "Constructors" in Mail::Box::Locker.

- $class-\>**new**(%options)

  Inherited, see "METHODS" in Mail::Box::Locker

  ```
   -Option    --Defined in       --Default
    expires     Mail::Box::Locker  1 hour
    file        Mail::Box::Locker  undef
    folder      Mail::Box::Locker  <C<undef>>
    method      Mail::Box::Locker  POSIX
    posix_file                     <C<undef>>
    timeout     Mail::Box::Locker  10
  ```

  - expires =\> $seconds

    - file =\> $file

    - folder =\> $folder

    - method =\> $name\|CLASS\|\\@names

    - posix\_file =\> FILENAME

    Alternative name for `"file"`, especially useful to avoid confusion when the multi-locker is used.

  - timeout =\> $seconds\|'NOTIMEOUT'

    ### Attributes

Extends "Attributes" in Mail::Box::Locker.

- $obj-\>**expires**( \[SECONDS\] )

  Inherited, see "Attributes" in Mail::Box::Locker

- $obj-\>**filename**( \[$filename\] )

  Inherited, see "Attributes" in Mail::Box::Locker

- $obj-\>**folder**( \[$folder\] )

  Inherited, see "Attributes" in Mail::Box::Locker

- $obj-\>**name**()

  Inherited, see "Attributes" in Mail::Box::Locker

- $obj-\>**timeout**( \[SECONDS\] )

  Inherited, see "Attributes" in Mail::Box::Locker

### Locking

Extends "Locking" in Mail::Box::Locker.

- $obj-\>**hasLock**()

  Inherited, see "Locking" in Mail::Box::Locker

- $obj-\>**isLocked**()

  Inherited, see "Locking" in Mail::Box::Locker

- $obj-\>**lock**()

  Inherited, see "Locking" in Mail::Box::Locker

- $obj-\>**unlock**()

  Inherited, see "Locking" in Mail::Box::Locker

### Error handling

Extends "Error handling" in Mail::Box::Locker.

- $obj-\>**AUTOLOAD**()

  Inherited, see "Error handling" in Mail::Reporter

- $obj-\>**notImplemented**()

  Inherited, see "Error handling" in Mail::Reporter

### Cleanup

Extends "Cleanup" in Mail::Box::Locker.

- $obj-\>**DESTROY**()

  Inherited, see "Cleanup" in Mail::Box::Locker

## DIAGNOSTICS

- Error: class $package does not implement method $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. Cast by `notImplemented()`

- Warning: folder $name already lockf'd.

  Cast by `lock()`

- Fault: unable to check lock file $file for $folder: $!

  To check whether the `$file` is used to flock a `$folder`, the file must be opened.  Apparently this fails, which does not mean that the folder is locked neither that it is unlocked. Cast by `isLocked()`

- Fault: unable to open POSIX lock file $file for $folder: $!

  For POSIX style locking, a `$folder` it must be opened, which does not succeed for the specified reason. Cast by `lock()`

- Fault: will never get a POSIX lock at $file for $folder: $!

  Tried to lock 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. Cast by `lock()`

## SEE ALSO

This module is part of Mail-Box version 4.02, built on April 10, 2026. Website: *http://perl.overmeer.net/CPAN/*

## LICENSE

For contributors see file ChangeLog.

This software is copyright (c) 2001-2026 by Mark Overmeer.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.