#!/usr/bin/perl
use strict;
use warnings;
use File::Spec;
use Cache::FileCache ();

unless ( @ARGV ) {
    my $script = (File::Spec->splitpath($0))[2];
    die "$script another_program -and -its -args\n"
      . "caches the output from the command and only prints if it diff
+ers fro"
      . "m the last time $script was run. This allows you to say `$scr
+ipt who"
      . "is -i somedomain.org` and only have output show up when the w
+hois ou"
      . "tput changes\n";
}

my $pid;
my $sleep_count = 0;
do {
    $pid = open KID_TO_READ, "-|", @ARGV;
    unless (defined $pid) {
        warn "cannot fork: $!";
        die "bailing out" if $sleep_count++ > 6;
        sleep 10;
    }
} until defined $pid;

my $self = File::Spec->rel2abs( $0 );
my $cache = Cache::FileCache->new( { namespace => $self } );
my $old = $cache->get( "@ARGV" );
my $new = do { local $/; <KID_TO_READ> };

if ($new ne $old) {
    print $new;
    $cache->set( "@ARGV", $new );
}
close KID_TO_READ or warn "kid exited $?";

[download]

In reply to uniq_exec.pl - filters duplicate program output by diotalevi

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.