Message-ID: <3E5C84F6.AE344C33@yahoo.com>
Date: Wed, 26 Feb 2003 04:12:22 -0500
From: CBFalconer <cbfalconer AT yahoo DOT com>
Organization: Ched Research
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To: djgpp-workers AT delorie DOT com
Subject: Re: Implementation of fchmod [PATCH]
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Reply-To: djgpp-workers AT delorie DOT com

Richard Dawe wrote:
> Eli Zaretskii wrote:
> >
... snip ...
> >
> > Call isatty on the handle; if it returns zero, the handle is
> > redirected.
> 
> But can we assume file descriptors 0, 1, etc. are actually
> standard handles? What happens if the program closes them and
> then opens some other file? I don't think we can reliably tell
> whether it's a standard handle. So we can't return the
> pipe-specific error.

I use "isatty(fileno(stdin))".  In fact, to allow incorporation in
standard C code (the reference to help is for the client program):

/* This is very likely to be non-portable
   DOES NOT check fp open for reading
   NULL fp is considered a keyboard here!
   With "gcc -W -Wall -ansi -pedantic" we can expect
   implicit declaration warnings for isatty and fileno.
   However the result should link correctly.
   If it always returns 0 the system still works
   but will not give the automatic help.
*/
static int akeyboard(FILE *fp)
{
#ifndef __TURBOC__  /* TC2 is peculiar */
# ifdef __STDC__
  /* This dirty operation allows gcc -ansi -pedantic */
  extern int fileno(FILE *fp);
  extern int isatty(int fn);
# endif
#endif
   return ((fp != NULL) && isatty(fileno(fp)));
} /* akeyboard */

-- 
Chuck F (cbfalconer AT yahoo DOT com) (cbfalconer AT worldnet DOT att DOT net)
   Available for consulting/temporary embedded and systems.
   <http://cbfalconer.home.att.net>  USE worldnet address!