CODEWITHSUNDEEP
perl
iDev
iDev

Reputation: 2431

Reload a perl script while running if the modification time changes

I have a perl script running at any given time and triggering another perl script if a specific condition is met else it sleeps for 1 min. Every time I have to make a modification to the main script and re-run it, I have to ensure no sub-script is running and then kill it and re-run.

So, have been looking if I can reload the perl script automatically based on the modification time. I came across the below link (code snippet shared below) and it works. But wondering, if this is the right way to do it? Any pointers?

Code Snippet here: (test.pl keeps on running and Worker.pm can be modified as needed)

Worker.pm:

    package Worker;

our $iteration = 1;

sub do_some_work {
    return if $iteration > 100;
    printf "$iteration Original\n";
    $iteration++;
    sleep 1;
    return 1;
}

sub save_state {
    return $iteration;
}

sub load_state {
    my $class = shift;
    $iteration = shift;
}
1;

test.pl

#!/usr/bin/env perl

use lib '.';
use Worker;

my $library_file = $INC{'Worker.pm'};
my $library_mtime = ( stat( $library_file ) )[9];

while ( Worker->do_some_work() ) {
    my $new_mtime = ( stat( $library_file ) )[9];
    next if $new_mtime == $library_mtime;

    $library_mtime = $new_mtime;

    eval {
        my $state = Worker->save_state();
        delete $INC{'Worker.pm'};
        require 'Worker.pm';
        Worker->load_state( $state );
    };
}

Source from: https://www.depesz.com/2015/01/21/reloading-of-perl-script-while-its-running/

Upvotes: 1

Views: 837

Answers (1)

ikegami
ikegami

Reputation: 385887

The simplest solution would be to restart the entire program.

Without external help (doesn't properly exit)

exec($^X, $0);

With external help (exits properly)

exit(254);

plus

#!/bin/sh
while true ; do
   program "$@"
   e=$?
   if [[ $e != 254 ]] ; then
      exit $e
   fi
done

Upvotes: 1

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