Re: bin/46021: xargs should keep still

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR bin/46021; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: bin/46021: xargs should keep still
Date: Tue, 14 Feb 2012 07:20:15 +0000

 On Tue, Feb 14, 2012 at 04:50:00AM +0000, jklowden%schemamania.org@localhost 
wrote:
  >     xargs writes error messages to standard error if the utility 
  >     it's executing exits with an error or on a signal.  E.g.:
  >     
  >     $ find /usr | xargs ls | head -1
  >     /usr/X11R7/bin/X
  >     xargs: ls terminated by SIGPIPE
  >     
  >     As the above example shows, the message is unwelcome and unnecessary.  
  > [...]
 
 I don't agree with your reasoning. Let's consider a similar and not
 uncommon case:
 
 First, create a program that always exits with a signal:
 
        % ./die
        Segmentation fault
        % 
 
 Now let's place it in a pipeline:
 
        % find /usr/include | ./die
        Segmentation fault
        % find /usr/include | ./die | cat
        Segmentation fault 
        % find /usr/include | xargs ./die 
        xargs: ./die terminated by SIGSEGV
        % find /usr/include | xargs ./die | cat
        xargs: ./die terminated by SIGSEGV
        % 
 
 Looks to me like the behavior is uniform across all four cases. xargs
 doesn't print the same message, but it's equivalent and printed in the
 same circumstances.
 
 With sh your argument is even weaker, as sh prints more:
 
        $ find /usr/include | ./die
        [1]   Broken pipe             find /usr/include |
              Segmentation fault      ./die
        $ find /usr/include | ./die | cat
        [1]   Broken pipe             find /usr/include |
              Segmentation fault      ./die |
              Done                    cat
        $ find /usr/include | xargs ./die
        xargs: ./die terminated by SIGSEGV
        $ find /usr/include | xargs ./die | cat
        xargs: ./die terminated by SIGSEGV
        $ 
 
 zsh is similar to sh.
 
 Maybe SIGPIPE should be handled differently from other signals, but
 the change you've proposed is definitely wrong.
  
 -- 
 David A. Holland
 dholland%netbsd.org@localhost