File::Pid - Pid File Manipulation

       Casey West, <casey@geeknest.com>.

         Copyright (c) 2005 Casey West.  All rights reserved.
         This module is free software; you can redistribute it and/or modify it
         under the same terms as Perl itself.

perl v5.34.0                                       2022-06-13                                     File::Pid(3pm)

       This software manages a pid file for you. It will create a pid file, query the process within to discover
       if it's still running, and remove the pid file.

   new
         my $pidfile = File::Pid->new;

         my $thisfile = File::Pid->new({
           file => '/var/run/daemon.pid',
         });

         my $thisfileandpid = File::Pid->new({
           file => '/var/run/daemon.pid',
           pid  => '145',
         });

       This constructor takes two optional parameters.

       "file" - The name of the pid file to work on. If not specified, a pid file located in
       "File::Spec->tmpdir()" will be created that matches "(File::Basename::basename($0))[0] . '.pid'". So, for
       example, if $0 is ~/bin/sig.pl, the pid file will be /tmp/sig.pl.pid.

       "pid" - The pid to write to a new pidfile. If not specified, $$ is used when the pid file doesn't exist.
       When the pid file does exist, the pid inside it is used.

   file
         my $pidfile = $pidfile->file;

       Accessor/mutator for the filename used as the pid file.

   pid
         my $pid = $pidfile->pid;

       Accessor/mutator for the pid being saved to the pid file.

   write
         my $pid = $pidfile->write;

       Writes the pid file to disk, inserting the pid inside the file.  On success, the pid written is returned.
       On failure, "undef" is returned.

   running
         my $pid = $pidfile->running;
         die "Service already running: $pid\n" if $pid;

       Checks to see if the pricess identified in the pid file is still running. If the process is still
       running, the pid is returned. Otherwise "undef" is returned.

   remove
         $pidfile->remove or warn "Couldn't unlink pid file\n";

       Removes the pid file from disk. Returns true on success, false on failure.

   program_name
       This is a utility method that allows you to determine what "File::Pid" thinks the program name is.
       Internally this is used when no pid file is specified.

       File::Pid - Pid File Manipulation

       perl.

         use File::Pid;

         my $pidfile = File::Pid->new({
           file => '/some/file.pid',
         });

         $pidfile->write;

         if ( my $num = $pidfile->running ) {
             die "Already running: $num\n";
         }

         $pidfile->remove;