From: Tanaka Akira <akr@...>
Date: 2010-02-06T12:07:56+09:00
Subject: [ruby-core:28076] Re: [Bug #2715] Optimization to avoid spawning 	shell in Kernel#system call should check for failure conditions

2010/2/6 Nobuyoshi Nakada <nobu@ruby-lang.org>:

> What's that you want to do?  In 1.9, the former returns nil,
> while the later returns false, and spawn and Process.spawn
> raise an Errno::ENOENT.

I guess he want to print the error message.
I think it is sane request.

In 1.9, this may be implemented as follows.

def system_with_error_message(str)
  if system(str) == nil
    command = str[/\S+/]
    STDERR.puts "#{command}: command not found"
  end
end
system_with_error_message("fail")
system_with_error_message("fail;")

However, we should not need such conditional
because the shell avoidance is an optimization.
We should not need to know optimizations in general.

>  # run "fail" command with no output
>  system("fail", out:"/dev/null", err:[:child, :out])

Shorter version:
  system("fail", [:out, :err]=>"/dev/null")
-- 
Tanaka Akira