annotate - annotate output with time elapsed

annotate

#!/usr/bin/perl

use POSIX qw(strftime);

$| = 1;

sub annotate_handle {
  my ($handle) = @_;
  my $start = time();
  while (<$handle>) {
    my $diff = time() - $start;
    my $h = int($diff / 3600);
    my $m = int (($diff % 3600) / 60);
    my $s = $diff % 60;
    my $ts = sprintf("%02d:%02d:%02d", $h, $m, $s);
    print "$ts $_";
  }
}

sub spawn {
  my (@args) = @_;
  my ($rh, $wh);
  pipe($rh, $wh);
  my $pid = fork();

  if (!defined($pid)) {
    die "unable to fork: $!\n";
  }
  if ($pid) { # parent
    close($wh);
    return $rh;
  } else {
    close($rh);
    open(STDOUT, ">&", $wh);
    open(STDERR, ">&", $wh);
    exec(@args) or die "unable to exec: $!";
  }
}

sub main {
  if (@ARGV) {
    my $fh = spawn(@ARGV);
    annotate_handle($fh);
  } else {
    annotate_handle(\*STDIN);
  }
}

main()