Path: utzoo!attcan!uunet!tektronix!psueea!parsely!bucket!servio!penneyj
From: penneyj@servio.UUCP (D. Jason Penney)
Newsgroups: comp.unix.questions
Subject: csh Rerouting stderr
Summary: Where Does it Put stderr?
Message-ID: <122@servio.UUCP>
Date: 10 May 89 17:56:49 GMT
Reply-To: penneyj@servio.UUCP (D. Jason Penney)
Organization: Servio Logic Development Corp.; Beaverton, OR
Lines: 57

I have a question that some one with Unix source should be able to
easily answer for me.

THE ENVIRONMENT: SunOS (or AIX) Unix.

THE SCENARIO: my program is fork()'ing another process which eventually
execve()'s a shell script.  Before the execve(), the program reroutes
stdout and stderr to a disk file:

fork();
...
setpgrp(0, getpid());
close(1); /* stdout */
close(2); /* stderr */
dup(creat("logfile", 0644); /* points 1 and 2 at logfile */
...
execve("script", argv, envp);

THE PROBLEM:

If script is as follows,

#! /bin/sh
frob

logfile contains
frob: not found

(Other more sophisticated tests show that stderr is indeed being
rerouted properly.)
If script is as follows,

#! /bin/csh
frob

nothing appears! (Other tests indicate that the writes to stderr are
trashing my address space!)

Workaround:  If script is as follows,

#! /bin/csh
(frob) |& cat

logfile contains
frob: Command not found.

THE QUESTION:  csh is obviously doing something "smart" with stderr.
Just what is going on?

Please reply directly to me -- if results are interesting enough, I
may post a followup.  Thank you in advance...

-- 
D. Jason Penney                  Ph: (503) 629-8383
Beaverton, OR 97006              uucp: ...ogccse!servio!penneyj
STANDARD DISCLAIMER:  Should I or my opinions be caught or killed, the
company will disavow any knowledge of my actions...