From: Martin DeMello <martindemello@...>
Date: 2006-11-13T23:18:16+09:00
Subject: waiting for multiple child processes to finish

Why does this not work (it waits for each process to finish before
launching the next):
-------------------------------------------------------------
$stdout.sync = true

10.times {|i|
  pid = Process.fork {
    puts "launching process #{i}"
    3.times {
      sleep 0.5
      puts "hello from process #{i}"
    }
  }
  Thread.new { Process.waitpid(pid) }.join
}

puts "done!"
-------------------------------------------------------------

but this does:
-------------------------------------------------------------
$stdout.sync = true

pids = []
10.times {|i|
  pids << Process.fork {
    puts "launching process #{i}"
    3.times {
      sleep 0.5
      puts "hello from process #{i}"
    }
  }
}

pids.each {|pid| Thread.new { Process.waitpid(pid) }.join }
puts "done!"
-------------------------------------------------------------