File::Flock::Retry - Yet another flock module

       perlancar <perlancar@cpan.org>

       Please    report    any    bugs     or     feature     requests     on     the     bugtracker     website
       <https://rt.cpan.org/Public/Dist/Display.html?Name=File-Flock-Retry>

       When  submitting  a  bug  or request, please include a test-file or a patch to an existing test-file that
       illustrates the bug or desired feature.

       Not yet tested on Windows. Some filesystems do not support inode?

       This software is copyright (c) 2021, 2019, 2017, 2015, 2014 by perlancar <perlancar@cpan.org>.

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

perl v5.36.0                                       2022-10-13                            File::Flock::Retry(3pm)

       This is yet another flock module. It is a more lightweight alternative to File::Flock with some other
       differences:

       •   OO interface only

       •   Autoretry (by default for 60s) when trying to acquire lock

           I prefer this approach to blocking/waiting indefinitely or failing immediately.

       Please visit the project's homepage at <https://metacpan.org/release/File-Flock-Retry>.

lock
       Usage:

        $lock = File::Flock::Retry->lock($path, \%opts)

       Attempt  to  acquire  an exclusive lock on $path. By default, $path will be created if not already exists
       (see "mode"). If $path is already locked by another process, will retry every  second  for  a  number  of
       seconds (by default 60). Will die if failed to acquire lock after all retries.

       Will automatically unlock if $lock goes out of scope. Upon unlock, will remove $path if it is still empty
       (zero-sized).

       Available options:

       •   mode

           Integer. Default: O_CREAT | O_RDWR.

           File  open mode, to be passed to Perl's "sysopen()". For example, if you want to avoid race condition
           between creating and locking the file, you might want to use "O_CREAT | O_EXCL | O_RDWR" to fail when
           the file already  exists.  Note  that  the  constants  are  available  after  you  do  a  "use  Fcntl
           ':DEFAULT';".

       •   retries

           Integer. Default: 60.

           Number of retries (equals number of seconds, since retry is done every second).

       •   shared

           Boolean. Default: 0.

           By  default,  an  exclusive  lock  (LOCK_EX)  is attempted. However, if this option is set to true, a
           shared lock (LOCK_SH) is attempted.

   unlock
       Usage:

        $lock->unlock

       Unlock. will remove lock file if it is still empty.

   release
       Usage:

        $lock->release

       Synonym for "unlock".

   handle
       Usage:

        my $fh = $lock->handle;

       Return the file handle.

       File::Flock::Retry - Yet another flock module

       File::Flock, a bit too heavy in terms of dependencies and startup overhead, for my taste. It  depends  on
       things like File::Slurp and Data::Structure::Util (which loads Digest::MD5, Storable, among others).

       File::Flock::Tiny  which  is also tiny, but does not have the autoremove and autoretry capability which I
       want. See also: <https://github.com/trinitum/perl-File-Flock-Tiny/issues/1>

       flock() Perl function.

       An alternative to flock() is just using sysopen() with O_CREAT|O_EXCL mode to create lock files. This  is
       supported on more filesystems (particularly network filesystems which lack flock()).

       Source repository is at <https://github.com/perlancar/perl-File-Flock-Retry>.

        use File::Flock::Retry;

        # try to acquire exclusive lock. if fail to acquire lock within 60s, die.
        my $lock = File::Flock::Retry->lock($file);

        # explicitly unlock
        $lock->release;

        # automatically unlock if object is DESTROY-ed.
        undef $lock;

       This document describes version 0.632 of File::Flock::Retry (from Perl distribution File-Flock-Retry),
       released on 2021-08-10.