=encoding utf8

=head1 NAME

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

=head1 INHERITANCE

 Mail::Box::Locker::Flock
   is a Mail::Box::Locker
   is a Mail::Reporter

=head1 SYNOPSIS

 See Mail::Box::Locker

=head1 DESCRIPTION

The C<::Flock> object locks the folder by creating an exclusive lock on
the file using the kernel's C<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 C<flock>.

Extends L<"DESCRIPTION" in Mail::Box::Locker|Mail::Box::Locker/"DESCRIPTION">.
 
=head1 METHODS

Extends L<"METHODS" in Mail::Box::Locker|Mail::Box::Locker/"METHODS">.
 
=head2 Constructors

Extends L<"Constructors" in Mail::Box::Locker|Mail::Box::Locker/"Constructors">.
 
=over 4

=item Mail::Box::Locker::Flock-E<gt>B<new>(%options)

 -Option --Defined in       --Default
  expires  Mail::Box::Locker  1 hour
  file     Mail::Box::Locker  undef
  folder   Mail::Box::Locker  <undef>
  log      Mail::Reporter     'WARNINGS'
  method   Mail::Box::Locker  'FLOCK'
  timeout  Mail::Box::Locker  10
  trace    Mail::Reporter     'WARNINGS'

=over 2

=item expires => SECONDS

=item file => FILENAME

=item folder => FOLDER

=item log => LEVEL

=item method => STRING|CLASS|ARRAY

=item timeout => SECONDS|'NOTIMEOUT'

=item trace => LEVEL

=back

=back

=head2 Attributes

Extends L<"Attributes" in Mail::Box::Locker|Mail::Box::Locker/"Attributes">.
 
=over 4

=item $obj-E<gt>B<expires>( [SECONDS] )

Inherited, see L<Mail::Box::Locker/"Attributes">

=item $obj-E<gt>B<timeout>( [SECONDS] )

Inherited, see L<Mail::Box::Locker/"Attributes">

=back

=head2 The Locker

Extends L<"The Locker" in Mail::Box::Locker|Mail::Box::Locker/"The Locker">.
 
=over 4

=item $obj-E<gt>B<filename>( [$filename] )

Inherited, see L<Mail::Box::Locker/"The Locker">

=item $obj-E<gt>B<folder>( [$folder] )

Inherited, see L<Mail::Box::Locker/"The Locker">

=item $obj-E<gt>B<name>()

Inherited, see L<Mail::Box::Locker/"The Locker">

=back

=head2 Locking

Extends L<"Locking" in Mail::Box::Locker|Mail::Box::Locker/"Locking">.
 
=over 4

=item $obj-E<gt>B<hasLock>()

Inherited, see L<Mail::Box::Locker/"Locking">

=item $obj-E<gt>B<isLocked>()

=item $obj-E<gt>B<lock>()

=item $obj-E<gt>B<unlock>()

Inherited, see L<Mail::Box::Locker/"Locking">

=back

=head2 Error handling

Extends L<"Error handling" in Mail::Box::Locker|Mail::Box::Locker/"Error handling">.
 
=over 4

=item $obj-E<gt>B<AUTOLOAD>()

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<addReport>($object)

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<defaultTrace>( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )

=item Mail::Box::Locker::Flock-E<gt>B<defaultTrace>( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<errors>()

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<log>( [$level, [$strings]] )

=item Mail::Box::Locker::Flock-E<gt>B<log>( [$level, [$strings]] )

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<logPriority>($level)

=item Mail::Box::Locker::Flock-E<gt>B<logPriority>($level)

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<logSettings>()

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<notImplemented>()

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<report>( [$level] )

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<reportAll>( [$level] )

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<trace>( [$level] )

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<warnings>()

Inherited, see L<Mail::Reporter/"Error handling">

=back

=head2 Cleanup

Extends L<"Cleanup" in Mail::Box::Locker|Mail::Box::Locker/"Cleanup">.
 
=over 4

=item $obj-E<gt>B<DESTROY>()

Inherited, see L<Mail::Box::Locker/"Cleanup">

=back

=head1 DIAGNOSTICS

=over 4

=item 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)

=item 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.

=item 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.

=item 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.

=item 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.

=back

=head1 SEE ALSO

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

=head1 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 F<http://dev.perl.org/licenses/>