Re: Creating PID file

On Sun, Apr 27, 2008 at 2:49 AM, Michael Barnes <MBarnes@[EMAIL PROTECTED]
>
wrote:
> My apologies.  I know this is a cross-platform group, and that is fine. 
However, if you are unable to understand simple Linux terminology, then it
is doubtful that you can help answer my question.  If the description is
nonsense to you, then please don't waste your or my time in an apparent
slam on my choice of operating systems.  If your reply represents the
general attitude of this list, then it looks like I've come to the wrong
place for assistance.
>
>  But, to simplify my request, a pid is a process id.  In Linux, the
command 'ps' will give a listing of process IDs.
>  I need the script to determine its own pid, then write that to a file.
snip

The variable $$ holds the PID for the current program*.  Typically a
pidfile is created in /var/run by saying something like

use strict;
use warnings;
use File::Basename;

BEGIN {
    our $program = basename $0;
    die "$program already running\n" if -f "/var/run/$program";
    open my $pidfile, ">", "/var/run/$program"
        or die "could not open /var/run$program: $!";
    print $pidfile "$$\n";
    close $pidfile;
}

#make sure the last thing done is the removal of the pidfile
#note: this happens even if we die
END {
    our $program;
    unlink("/var/run/$program")
        or die "could not delete /var/run/$program";
}

#the rest of your code

There are also a few modules on CPAN that automate this to a certain
extent for you: Proc::Pidfile**, File::Pid***, and
File::Pid::Quick****.

* see perldoc perlvar or
http://perldoc.perl.org/perlvar.html#$PROCESS_ID
for more information
** http://search.cpan.org/dist/Proc-Pidfile/Pidfile.pm
*** http://search.cpan.org/dist/File-Pid/lib/File/Pid.pm
**** http://search.cpan.org/dist/File-Pid-Quick/Quick.pm
-- 
Chas. Owens
wonkden.net
The most im****tant skill a programmer can have is the ability to read.