Issue #2715 has been updated by kosaki (Motohiro KOSAKI).


Hmm...

As akr-san described, some shells have tail invocation optimization. Thus, even if ruby doesn't have shell invocation optimization, caller can't assume that spawned process is neither child nor grand child.

Therefore, if some tests were fail, it is certainly test mistake. I still think we can remove the shell invocation optimization. It is a source of confusion and I dislike it.

# Of cource, it shouldn't be backported 1.9.x.
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Feature #2715: Optimization to avoid spawning shell in Kernel#system call should check for failure conditions
https://bugs.ruby-lang.org/issues/2715#change-27023

Author: taw (Tomasz Wegrzanowski)
Status: Feedback
Priority: Normal
Assignee: akr (Akira Tanaka)
Category: core
Target version: 


=begin
 This is an old issue, I think going all the way back to Perl's system().
 
 Kernel#system is supposed to spawn shell and pass its argument to shell process just like C system(); except it's optimized for a common case of very simple argument, in which case Ruby (like Perl) simply does fork and exec of the string passed, split on whitespace.
 
 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).
 
 rb_f_system code for VMS and Windows uses different code paths, so I don't know if it's also affected or not.
 
 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
=end



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