#!/usr/bin/ruby

# Batch process distributer (per-argument) for multi-core systems, version 1.0
#
# Copyright Clay Barnes (clay@hci-matters.com)
# Licenced under the GNU Public Licence Version 3 or later
# 
# If you find this useful (or find a bug), please drop me an email. I know it's
# not feature complete, but hey, quick 'n' dirty does the job sometimes!

def print_usage; puts "Usage: distributer num_processes command var1 [ var2... ]\nUse %VAR to reference the current variable (ex. echo %VAR)"; exit; end
def print_seperator; puts "\n================================================================================\n\n"; end

if ARGV.size < 3 then print_usage end # Too few arguments.
begin	# Initalize variables.  Errors are assumed to be the user's fault ;-)
	num_threads = 0 + ARGV[0].to_i
	if num_threads<1 then print_usage; exit; end
	puts "Number of concurrent processes: " + num_threads.to_s
	command = ARGV[1]
	puts "Using command '" + command.gsub("%VAR", "[VARIABLE_HERE]")+"'"
	variables = ARGV[2..-1]
	puts "Using the following variables:\n"+"'"+ variables*"', '" +"'"
	print_seperator
rescue	# Oops, bug out!
	print_usage
end
begin	# Parallelize [num_threads] processes.
	index = 0 # Index of current variable
	while num_threads > 0 and variables[index]
		puts "Starting: " + command.gsub("%VAR",variables[index])
		print_seperator
		Process.fork{system(command.gsub("%VAR",variables[index]))}
		num_threads = num_threads - 1
		index = index + 1
	end
	while true
		Process.wait(-1, 0) # Whenever a process exits, spawn a new one.
		if variables[index] # Quite creating processes upon nil!
			puts "Starting: "+command.gsub("%VAR",variables[index])
			print_seperator
			Process.fork{system(command.gsub("%VAR",variables[index]))}
			index = index + 1
		end
	end
rescue Errno::ECHILD # Once finished creating processes, and all have exited.
	puts "All processes completed!"
end