spork

#!/usr/bin/env perl
use threadeach;
use warnings;
use strict;
use Getopt::Long qw(:config bundling);
use Switch;

my $username=getlogin || getpwuid($<);
my $threaded=0;
my $filename="";
my $debug	=0;
my $notint	=0; #not interactive - shortcut for threading and running without needing interaction

GetOptions (
	'username|u=s'	=> \$username,
	'threaded|t:1'	=> \$threaded,
	'filename|f=s'	=> \$filename,
	'debug|d:1'		=> \$debug,
	'notinteractive|n'=> \$notint,
	'help|h'		=> \&usage,
	);

my $command=shift || usage();

#check for passed values - which will be used as a list of machine names in lieu of the filename arg
my @lines=();
if(!-t STDIN){@lines=<>;}
if(!@lines)
{
	open(F,$filename)
		or die("Couldn't open file $filename for reading: $!\n");
	@lines=<F>;
	close(F)
		or die("Couldn't close filehandle for $filename: $!\n");
}
if(!@lines){warn "No machine names found\n";usage();}

#get rid of newlines, empty lines, and whitespace in lines
chomp(@lines);
@lines=map{$a=$_;$a=~s/\s+//g;$a}@lines;
my @tmp=();foreach my $l(@lines){push(@tmp,$l) if $l;}
@lines=@tmp;

print "username=$username, threaded=$threaded, filename=$filename, command=$command\n" if $debug;
print "Host list:".join(",",@lines)."\n" if $debug;

#get the difference between the longest and shortest one (for pretty formatting)
my $longest=(sort(map {length($_)}@lines))[-1];

#decide how to run, threaded or not, and how many
switch($threaded)
{
	case -1 			
	{
		threadall my $l(@lines){
			runcmd_not_int($l);
		}
	}
	case 1				
	{
		threadeach my $l(@lines)
		{
			runcmd_not_int($l);
		}	
	}	
	case {$threaded>0}	
	{
		threadeach::threadsome(\&runcmd_not_int,$threaded,@lines);
	}
	else	{run_looped()}
}

sub run_looped
{
	my $iserr=shift ||0;
	warn "Running in serial because of no threadeach library\n" if $iserr;
	 foreach my $line(@lines)
	 {
		if($notint){&runcmd_not_int($line,$command);}
		else{&runcmd_int($line,$command);}
	}
}

sub runcmd_int
{
	my $host=shift || return;
	my $pad=" "x ($longest-length($host));
	my $cmd="ssh $username\@$host \"$command\"";
	print $cmd if $debug;
	system($cmd);
}
#if it's not interactive, we can make the output nicer.  :)
sub runcmd_not_int
{
	my $host=shift || return;
	open(CMD,"ssh $username\@$host \"$command\" |")
		or die("Couldn't open command: $!");
	my $pad=" "x ($longest-length($host));
	while(<CMD>)
	{
		my $ret=$_;
		chomp($ret);
		print "$host:$pad$ret\n";
	}
}

sub usage
{
	print <<cEND;
Usage: $0 -f <filename> "command to run on remote host"
Options:
  -u/--username username to run as
  -t/--threaded Whether to run as threaded, optionally with the # of threads, or -1 to run all
  -f/--filename filename to use as list of hosts
Example:
  $0 -d -t 8 -u root -f myhostsfile "uptime"
    will go to all the hosts listed in myhostsfile and run the "uptime" command with max 8 parallel threads
  grep nameserver /etc/resolv.conf | awk '{print \$2}' | $0 'host google.com'
    will go to all the nameservers in resolv.conf one at a time and run 'host google.com' on them
  ./$0 -f hostlist -t-1 -uroot uptime
    will go to all machines in "hostlist" and run "uptime" with as many parallel threads as there are hosts
cEND

exit();
}