#!/usr/bin/perl -w
use strict;
$|++;

use vars qw/ $opt_d $opt_v /;

my $Version = '$Id: runmany,v 1.2 2002/12/21 06:42:42 felicity Stab $';

use Getopt::Std;
&getopts("dv") || &Usage;

&Usage if $#ARGV != 1; # sanity check on args present and accounted for
my($proc,$limit) = splice @ARGV, 0, 2;

print STDERR "Cmd: \"$proc\"\nNum: $limit\n" if $opt_v || $opt_d;

my $started = 0;
my $finished = 0;
while (<>) {
		 chomp;
		 unless (fork()) {
				 my $cmd;
		 		 if ($proc =~ m/%s/) {
		 		 		 ($cmd = $proc) =~ s/%s/$_/g;
		 		 } else {
		 		 		 $cmd = "${proc} $_";
		 		 }		 		 
				 print STDERR "Running '$cmd'\n" if ( $opt_v || $opt_d );
		 		 exec $cmd;
				 # we should never get here
				 die "exec $cmd failed!: $!\n";
		 }
		 ++$started;
		 my $running = $started - $finished;
		 print STDERR "$started $finished\n" if $opt_d;
		 if ($limit <= $running) {
		 		 wait;
		 		 ++$finished;
		 }
}

# wait for last children and exit clean
until ($finished == $started) {
		 print STDERR "Final wait: $started  $finished\n" if $opt_d;
		 wait;
		 ++$finished;
}
exit 0;

sub Usage
{
		 print "\n$Version\n\n"
		 . "Usage:\n"
		 . "  runmany [options] <cmd string> <count>\n"
		 . "\n"
		 . "lines are read from stdin, and the values read are used to replace\n"
		 . "any instances of \"%s\" in the <cmd string>. Copies of the modified\n"
		 . "command are started until <count> copies are running, then a new copy\n"
		 . "is started every time a command process ends.\n"
		 . "\n"
		 . "This is useful when more than one item may be processed at a time, but\n"
		 . "processing all possible commands at once could / would overload the system.\n"
		 . "\n"
		 . "Options:\n"
		 . "  -v    Verbose, output the command and count when starting\n"
		 . "  -d    Debug. Output a bunch of data while running.\n"
		 . "\n"
		 . "Example:\n"
		 . "  ls | grep '\.o\$' | runmany \"gzip -8v %s\" 3\n"
		 . "\n"
		 . "would compress three files at a time (presumable on a system with at\n"
		 . "least that many processors.\n"
		 . "\n"
		 . "Author: Bill Davidsen <davidsen\@tmr.com>\n"
		 . "\n";

		 exit 1;
}