chronic

   1 #!/usr/bin/perl
   2
   3 =head1 NAME
   4
   5 chronic - runs a command quietly unless it fails
   6
   7 =head1 SYNOPSIS
   8
   9 chronic COMMAND...
  10
  11 =head1 DESCRIPTION
  12
  13 chronic runs a command, and arranges for its standard out and standard
  14 error to only be displayed if the command fails (exits nonzero or crashes).
  15 If the command succeeds, any extraneous output will be hidden.
  16
  17 A common use for chronic is for running a cron job. Rather than
  18 trying to keep the command quiet, and having to deal with mails containing
  19 accidental output when it succeeds, and not verbose enough output when it
  20 fails, you can just run it verbosely always, and use chronic to hide
  21 the successful output.
  22
  23         0 1 * * * chronic backup # instead of backup >/dev/null 2>&1
  24
  25 =head1 AUTHOR
  26
  27 Copyright 2010 by Joey Hess <id@joeyh.name>
  28
  29 Original concept and "chronic" name by Chuck Houpt.
  30
  31 Licensed under the GNU GPL version 2 or higher.
  32
  33 =cut
  34
  35 use warnings;
  36 use strict;
  37 use IPC::Run qw( start pump finish timeout );
  38
  39 if (! @ARGV) {
  40         die "usage: chronic COMMAND...\n";
  41 }
  42
  43 my ($out, $err);
  44 my $h = IPC::Run::start \@ARGV, \*STDIN, \$out, \$err;
  45 $h->finish;
  46 my $ret=$h->full_result;
  47
  48 if ($ret >> 8) { # child failed
  49         showout();
  50         exit ($ret >> 8);
  51 }
  52 elsif ($ret != 0) { # child killed by signal
  53         showout();
  54         exit 1;
  55 }
  56 else {
  57         exit 0;
  58 }
  59
  60 sub showout {
  61         print STDOUT $out;
  62         print STDERR $err;
  63 }