#! /usr/local/bin/perl
# default number of processes is 8, 
# but is resettable using the -m argument
#
# usage:
# muxssh [-m max] [-v] [-l username] command [args ...] <list_of_machines
#
# example:
#      muxssh /bin/arch <machines
#      muxssh -m 10 /bin/arch <machines
#      muxssh -v -l staff df -t 4.2 <machines
#
# ------------------------------
# subroutine definitions   ....

sub getswitches {
  # parse arguments
  while ($ARGV[0] =~ /^-/) {
    $ARGV[0] =~ /^-v/ && ($verbose++,shift(@ARGV),next);
    $ARGV[0] =~ /^-m/ && (shift(@ARGV),$maxpids = shift(@ARGV), next);
    $ARGV[0] =~ /^-l/ && (shift(@ARGV),$remoteuser = "-l " . shift(@ARGV), next);
    last;
  }
}

sub wait {
  if ( $verbose ) {
    print "process $$ called wait with ",&alive," alive:";
    print join(' ',values(%pids)),"\n";
  }

  my($somepid);
  while ($somepid = wait) {
    if (defined $pids{$somepid}) {
      print "wait saw $pids{$somepid}\n" if ( $verbose );
      return delete $pids{$somepid};
    } else {
      print "wait saw $somepid?\n" if ( $verbose );
    }
  }
  warn "wait: nobody to wait on: $!";
}

sub alive {
  return scalar(keys %pids);
}

#--------------
# main routine
#

$|=1;				# flush buffers on a line-by-line basis
$verbose = 0;			# assume verbose is off
$maxpids = 8;			# default maximum number of processes
$remoteuser=""; 
%pids = ();			# zero out the pids
&getswitches();			# get any switches/changes to defaults
die "Must specify a command to be executed!\n" unless ( @ARGV );
print "remote user is $remoteuser\n" if ( $verbose && $remoteuser );
print "Max number of processes is $maxpids\n" if ( $verbose );

while ($machine = <STDIN>) {
  chomp $machine;
  print "forking for $machine with ",&alive," alive\n" if ( $verbose );
  &wait() if &alive >= $maxpids;
  $pid = fork;
  die "fork: $!" unless defined $pid;
  if ($pid) { # parent
    $pids{$pid} = $machine;
  } else {
    $command = "ssh -f -n -q -c blowfish -x -o \'StrictHostKeyChecking=no\'";
    $params = "$machine $remoteuser \'@ARGV\' 2>&1";
    open(COM,"$command $params|") || die "Can't issue command:$!";
    print "$machine: $_" while ( <COM> );
    close(COM);
    exit 0;
  }
}
&wait() while &alive > 0;