[ruby-core:28074] Re: [Bug #2715] Optimization to avoid spawning shell in Kernel#system call should check for failure conditions

Hi,

At Sat, 6 Feb 2010 06:55:09 +0900,
Tomasz Wegrzanowski wrote in [ruby-core:28072]:
> This almost works, except shell error reporting is not
> duplicated. If command doesn't exist, shell would print an
> error message on stderr, while Ruby like Perl fails silently.
> 
> Problem is present in all versions of Ruby including 1.8.7 and 1.9.1.
> 
> To reproduce:
> $ ruby -e 'system "fail"'
> $ ruby -e 'system "\"\"fail"'
> sh: fail: command not found

> Output of both commands should be identical (or at least
> close enough, details of error message might differ by Unix
> flavor).

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.

In addtion, system and spawn in 1.9 have been improved very
much, so you don't need to use sh for redirection.

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

> I wrote a bit more about background of this issue on my blog:
> http://t-a-w.blogspot.com/2010/02/what-is-all-this-perl-doing-in-my-ruby.html

Please describe the rationale briefly on the BTS, not separated
blog.

-- 
Nobu Nakada