#!/usr/bin/env perl

use strict;
use warnings;

use Parallel::ForkManager;

### hash keys ###
my $HOST = q/host/;
my $START = q/start/;

### cmd line options
my $CMD_OPT  = q/-c/;
my $USER_OPT = q/-u/;
my $SSH_OPT  = q/-s/;
my $EVAL_OPT = q/-e/;
my $HELP_OPT = q/-h/;
my $TIMEOUT_OPT = q/-t/;

### defaults
my $ssh  = my $ssh_default  = q/ssh/;
my $cmd  = my $cmd_default  = q/uptime/;
my $user = my $user_default = q/murphy/;
my $timeout = 90;

### process cmd line
my @temp_args;

while (@ARGV)
{
    if ($ARGV[0] =~ /^$CMD_OPT$/)
    {
        shift;
        if (exists $ARGV[0])
        {
            $cmd = shift;
            next;
        }
        else
        {
            warn "Error: option $CMD_OPT requires an argument\n";
            usage();
        }
    }

    if ($ARGV[0] =~ /^$USER_OPT$/)
    {
        shift;
        if (exists $ARGV[0])
        {
            $user = shift;
            next;
        }
        else
        {
            warn "Error: option $USER_OPT requires an argument\n";
            usage();
        }
    }

    if ($ARGV[0] =~ /^$SSH_OPT$/)
    {
        shift;
        if (exists $ARGV[0])
        {
            $ssh = shift;
            next;
        }
        else
        {
            warn "Error: option $SSH_OPT requires an argument\n";
            usage();
        }
    }

    if ($ARGV[0] =~ /^$TIMEOUT_OPT$/)
    {
        shift;
        if (exists $ARGV[0])
        {
            $timeout = shift;
            next;
        }
        else
        {
            warn "Error: option $TIMEOUT_OPT requires an argument\n";
            usage();
        }
    }

    if ($ARGV[0] =~ /^$EVAL_OPT$/)
    {
        shift;
        if (exists $ARGV[0])
        {
            my $eval_string = shift;
            my @result;
            {
#                no strict 'subs';
                @result = eval "$eval_string";
                print "<", join(', ', @result), ">\n";
                die ($@) if $@;
#                print "\n";
            }
            push @ARGV, @result if @result;
            next;
        }
        else
        {
            warn "Error: option $EVAL_OPT requires an argument\n";
            usage();
        }
    }

    if ($ARGV[0] =~ /^$HELP_OPT/)
    {
        usage();
    }

    push @temp_args, shift;
}

@ARGV = @temp_args;

### setup default host list
my $host_base = q/camhyd/;
my $blade_base = q/mur/;
my $blade_sign = q/b/;
my @hosts = map { $host_base . $_ } qw(tc01);

for my $rack ('001'..'003')
{
    for my $blade (0..7)
    {
        push @hosts, "${host_base}${blade_base}${rack}${blade_sign}${b
+lade}";
    }
}

### override from cmd line
if (@ARGV)
{
    @hosts = @ARGV;
}

# save child pids here
my %children;

# create new manager, limit number of parallel processes
my $pm = new Parallel::ForkManager(10); # limit to 10 parallel process
+es

for my $host (sort @hosts)
{
    if (my $pid = $pm->start) {
      $children{$pid}{$HOST} = $host;
      $children{$pid}{$START} = time();
      next;
    }
    ### child section ###
    alarm($timeout); # die after elapsed time in child

    my @result = qx/$ssh ${user}\@$host '$cmd'/;

    my $prefix = sprintf " %20s)  ", $host;
    my $message;
    $message = sprintf "%s\n", '*' x 20 if (@result != 1);
    for my $r (@result) {
        $message .= "$prefix$r";
    }
    print "$message\n";
    $pm->finish; # do the exit in the child process
}
$pm->wait_all_children;

exit;

sub usage
{
    warn "Usage: $0 [-s ssh_cmd] [-u user] [-c cmd] [hosts...]\n\n";
    warn "    where:\n\n";
    warn "    $SSH_OPT ssh_cmd    ssh-type cmd to use (default: $ssh_d
+efault)\n";
    warn "    $USER_OPT user       username for the ssh_cmd (default: 
+$user_default)\n";
    warn "    $CMD_OPT cmd        remote shell command to use on the h
+osts (default: $cmd_default)\n";
    warn "    $EVAL_OPT cmd        eval arguments, such as ranges (ex:
+ $EVAL_OPT 'glob(\"camhydmur00{1,2,3}b{0,1,2,3,4,5,6,7}\")')\n";
    warn "    $TIMEOUT_OPT cmd        timeout in seconds before parent
+ reaps children\n";
    warn "    hosts...      hostnames for the remote shell command\n";
    warn "    $HELP_OPT            usage (this output)\n";
    warn "\n";
    warn "It is assumed that ssh key exchange has already been setup.\
+n";
    die "\n";
}
[download]

Typical run looks like this:

my_machine> net.pl -c 'date' camhydmur001b{1,2,3}
       camhydmur001b3)  Fri May 10 12:15:58 GMT 2013

       camhydmur001b1)  Fri May 10 12:15:58 GMT 2013

       camhydmur001b2)  Fri May 10 12:15:58 GMT 2013
[download]

However, when there are errors, I haven't figured out how to assign them to the corresponding host:

my_machine> net.pl -c 'ls /junk' camhydmur001b{1,2,3}
ls: cannot access /junk: No such file or directory
********************

ls: cannot access /junk: No such file or directory
********************

ls: cannot access /junk: No such file or directory
********************
[download]