Feature #2715

Optimization to avoid spawning shell in Kernel#system call should check for failure conditions

Added by taw (Tomasz Wegrzanowski) over 10 years ago. Updated over 2 years ago.

Target version:


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:


Related issues

Related to Ruby master - Feature #3426: exec doesn't allow command lines which begin with an env variable assignmentRejectedmame (Yusuke Endoh)06/11/2010Actions
Related to Ruby master - Feature #4477: Kernel:exec and backtick (`) don't work for certain system commandsClosedakr (Akira Tanaka)03/07/2011Actions

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