ruby-paralell

#!/usr/bin/ruby
#
# $ ./ruby-paralell echo 2 test <<EOLX
# first
# second
# third
# EOL
# [2192]+ echo first test
# [2193]+ echo second test
# first test
# second test
# [2194]+ echo third test
# third test
 
require 'shellwords'

# Kill spawned processes on failure
trap("SIGINT") { exit! }

# "rsync -a --del"
command_begin = Shellwords.escape ARGV.shift

## source-dir <= stdin
process_max_count = ARGV.shift.to_i

# "target-host:/dir/"
command_end = Shellwords.escape ARGV.shift

######################################

def failed? status
  unless status.success?
    puts "[#{status.pid}] Failed!"
    return true
  end
end

def check_exited processes
  failure_occured = nil

  processes.reject! do |pid|
    if exited = Process.waitpid(pid, Process::WNOHANG)
      failure_occured = failed?($?) or failure_occured
    end

    exited
  end

  if failure_occured
    wait_for_all processes
    abort
  end
end

def wait_for_all processes
  processes.each do |pid|
    Process.wait pid
    failed? $?
  end

  processes.clear
end

######################################

processes = Array.new

# "source-directory"
ARGF.each do |variable_arg|
  variable_arg = Shellwords.escape variable_arg.chomp

  command = [command_begin, variable_arg, command_end]
              .join(' ')

  while processes.count >= process_max_count
    sleep 0.1
    check_exited processes
  end

  processes << spawn(command)
  puts "[#{processes.last}]+ #{command}"
end

wait_for_all processes
exit