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From: jik@athena.mit.edu (Jonathan I. Kamens)
Newsgroups: comp.unix.questions
Subject: Re: Redirection of stderr
Keywords: stderr
Message-ID: <1991Mar14.225058.13507@athena.mit.edu>
Date: 14 Mar 91 22:50:58 GMT
References: <574@dprmpt.UUCP> <1991Mar14.220650.11736@athena.mit.edu>
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  Someone has pointed out to me in E-mail that assigning to stderr as I
indicated in my previous message won't work on many systems because of the way
stderr is defined.

  There are ways to get around this.  One of them, a rather gross method that
will nonetheless work on many systems, is to assign to stderr like this:

    *(stderr) = *(value to assign)

e.g.

    *(stderr) = *(fopen(error_file, "w"));

  However, this won't work if FILE * is an opaque type whose contents are not
spelled out for the compiler in <stdio.h>.

  It is possible to replace stderr with a file doing something like this:

    freopen(error_file, "w", stderr);

However, if you do things this way, I can't see any way to put the original
stderr back in place -- there is no "fdreopen".  That's unfortunate.

-- 
Jonathan Kamens			              USnail:
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jik@Athena.MIT.EDU				Allston, MA  02134
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