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.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
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.IX Title "Mail::Box::Locker::Flock 3"
.TH Mail::Box::Locker::Flock 3 2026-04-11 "perl v5.42.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
Mail::Box::Locker::Flock \- lock a folder using kernel file\-locking
.SH INHERITANCE
.IX Header "INHERITANCE"
.Vb 3
\& Mail::Box::Locker::Flock
\&   is a Mail::Box::Locker
\&   is a Mail::Reporter
.Ve
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&  See the generic Mail::Box::Locker interface
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
The \f(CW\*(C`::Flock\*(C'\fR object locks the folder by creating an exclusive lock on
the file using the kernel\*(Aqs \f(CW\*(C`flock\*(C'\fR facilities.  This lock is created
on a separate file\-handle to the folder file, so not the handle which
is reading.
.PP
File locking does not work in some situations, for instance for
operating systems do not support \f(CW\*(C`flock\*(C'\fR.
.PP
Extends "DESCRIPTION" in Mail::Box::Locker.
.SH METHODS
.IX Header "METHODS"
Extends "METHODS" in Mail::Box::Locker.
.SS Constructors
.IX Subsection "Constructors"
Extends "Constructors" in Mail::Box::Locker.
.ie n .IP $class\->\fBnew\fR(%options) 4
.el .IP \f(CW$class\fR\->\fBnew\fR(%options) 4
.IX Item "$class->new(%options)"
Inherited, see "METHODS" in Mail::Box::Locker
.Sp
.Vb 6
\& \-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  \*(AqFLOCK\*(Aq
\&  timeout  Mail::Box::Locker  10
.Ve
.RS 4
.ie n .IP "expires => $seconds" 2
.el .IP "expires => \f(CW$seconds\fR" 2
.IX Item "expires => $seconds"
.PD 0
.ie n .IP "file => $file" 2
.el .IP "file => \f(CW$file\fR" 2
.IX Item "file => $file"
.ie n .IP "folder => $folder" 2
.el .IP "folder => \f(CW$folder\fR" 2
.IX Item "folder => $folder"
.ie n .IP "method => $name|CLASS|\e@names" 2
.el .IP "method => \f(CW$name\fR|CLASS|\e@names" 2
.IX Item "method => $name|CLASS|@names"
.ie n .IP "timeout => $seconds|\*(AqNOTIMEOUT\*(Aq" 2
.el .IP "timeout => \f(CW$seconds\fR|\*(AqNOTIMEOUT\*(Aq" 2
.IX Item "timeout => $seconds|'NOTIMEOUT'"
.PD
.RE
.RS 4
.RE
.SS Attributes
.IX Subsection "Attributes"
Extends "Attributes" in Mail::Box::Locker.
.ie n .IP "$obj\->\fBexpires\fR( [SECONDS] )" 4
.el .IP "\f(CW$obj\fR\->\fBexpires\fR( [SECONDS] )" 4
.IX Item "$obj->expires( [SECONDS] )"
Inherited, see "Attributes" in Mail::Box::Locker
.ie n .IP "$obj\->\fBfilename\fR( [$filename] )" 4
.el .IP "\f(CW$obj\fR\->\fBfilename\fR( [$filename] )" 4
.IX Item "$obj->filename( [$filename] )"
Inherited, see "Attributes" in Mail::Box::Locker
.ie n .IP "$obj\->\fBfolder\fR( [$folder] )" 4
.el .IP "\f(CW$obj\fR\->\fBfolder\fR( [$folder] )" 4
.IX Item "$obj->folder( [$folder] )"
Inherited, see "Attributes" in Mail::Box::Locker
.ie n .IP $obj\->\fBname\fR() 4
.el .IP \f(CW$obj\fR\->\fBname\fR() 4
.IX Item "$obj->name()"
Inherited, see "Attributes" in Mail::Box::Locker
.ie n .IP "$obj\->\fBtimeout\fR( [SECONDS] )" 4
.el .IP "\f(CW$obj\fR\->\fBtimeout\fR( [SECONDS] )" 4
.IX Item "$obj->timeout( [SECONDS] )"
Inherited, see "Attributes" in Mail::Box::Locker
.SS Locking
.IX Subsection "Locking"
Extends "Locking" in Mail::Box::Locker.
.ie n .IP $obj\->\fBhasLock\fR() 4
.el .IP \f(CW$obj\fR\->\fBhasLock\fR() 4
.IX Item "$obj->hasLock()"
Inherited, see "Locking" in Mail::Box::Locker
.ie n .IP $obj\->\fBisLocked\fR() 4
.el .IP \f(CW$obj\fR\->\fBisLocked\fR() 4
.IX Item "$obj->isLocked()"
Inherited, see "Locking" in Mail::Box::Locker
.ie n .IP $obj\->\fBlock\fR() 4
.el .IP \f(CW$obj\fR\->\fBlock\fR() 4
.IX Item "$obj->lock()"
Acquire a lock on the folder.
Improves base, see "Locking" in Mail::Box::Locker
.ie n .IP $obj\->\fBunlock\fR() 4
.el .IP \f(CW$obj\fR\->\fBunlock\fR() 4
.IX Item "$obj->unlock()"
Inherited, see "Locking" in Mail::Box::Locker
.SS "Error handling"
.IX Subsection "Error handling"
Extends "Error handling" in Mail::Box::Locker.
.ie n .IP $obj\->\fBAUTOLOAD\fR() 4
.el .IP \f(CW$obj\fR\->\fBAUTOLOAD\fR() 4
.IX Item "$obj->AUTOLOAD()"
Inherited, see "Error handling" in Mail::Reporter
.ie n .IP $obj\->\fBnotImplemented\fR() 4
.el .IP \f(CW$obj\fR\->\fBnotImplemented\fR() 4
.IX Item "$obj->notImplemented()"
Inherited, see "Error handling" in Mail::Reporter
.SS Cleanup
.IX Subsection "Cleanup"
Extends "Cleanup" in Mail::Box::Locker.
.ie n .IP $obj\->\fBDESTROY\fR() 4
.el .IP \f(CW$obj\fR\->\fBDESTROY\fR() 4
.IX Item "$obj->DESTROY()"
Inherited, see "Cleanup" in Mail::Box::Locker
.SH DIAGNOSTICS
.IX Header "DIAGNOSTICS"
.ie n .IP "Error: class $package does not implement method $method." 4
.el .IP "Error: class \f(CW$package\fR does not implement method \f(CW$method\fR." 4
.IX Item "Error: class $package does not implement method $method."
Fatal error: the specific \f(CW$package\fR (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 \f(CWnotImplemented()\fR
.ie n .IP "Warning: folder $name already flocked." 4
.el .IP "Warning: folder \f(CW$name\fR already flocked." 4
.IX Item "Warning: folder $name already flocked."
The folder is already locked, but you attempt to lock it again.  The
behavior of double flock\*(Aqs is platform dependent, and therefore should
not be attempted.  The second lock is ignored (but the unlock isn\*(Aqt).
Cast by \f(CWlock()\fR
.ie n .IP "Fault: unable to check lock file $file for $folder: $!" 4
.el .IP "Fault: unable to check lock file \f(CW$file\fR for \f(CW$folder:\fR $!" 4
.IX Item "Fault: unable to check lock file $file for $folder: $!"
To check whether the \f(CW$file\fR is used to \f(CW\*(C`flock\*(C'\fR a \f(CW$folder\fR, the file must be
opened.  Apparently this fails, which does not mean that the folder is
locked neither that it is unlocked.
Cast by \f(CWisLocked()\fR
.ie n .IP "Fault: unable to open flock file $file for $folder: $!" 4
.el .IP "Fault: unable to open flock file \f(CW$file\fR for \f(CW$folder:\fR $!" 4
.IX Item "Fault: unable to open flock file $file for $folder: $!"
For \f(CW\*(C`flock\*(C'\fR\-ing a \f(CW$folder\fR it must be opened, which does not succeed for the
specified reason.
Cast by \f(CWlock()\fR
.ie n .IP "Fault: will never get a flock at $file for $folder: $!" 4
.el .IP "Fault: will never get a flock at \f(CW$file\fR for \f(CW$folder:\fR $!" 4
.IX Item "Fault: will never get a flock at $file for $folder: $!"
Tried to \f(CW\*(C`flock\*(C'\fR the \f(CW$folder\fR, 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 \f(CWlock()\fR
.SH "SEE ALSO"
.IX Header "SEE ALSO"
This module is part of Mail\-Box version 4.02,
built on April 10, 2026. Website: \fIhttp://perl.overmeer.net/CPAN/\fR
.SH LICENSE
.IX Header "LICENSE"
For contributors see file ChangeLog.
.PP
This software is copyright (c) 2001\-2026 by Mark Overmeer.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.