From:	Eric Backus <ericb AT lsid DOT hp DOT com>
Subject:	Re: hello!
To:	crimson AT wpi DOT WPI DOT EDU
Date:	Tue, 8 Jun 93 10:03:09 PDT
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu (djgpp)
Mailer:	Elm [revision: 66.25]

> I would like to throw a question out to the masses:
> 
>    binary file i/o.
> 
> Anyone had any trouble with it?  Have I just plain done something brain 
> damaged?  or is it under the heading of 'vagaries of messy-dos'?  Specifics
> to those interested/knowledgeable in this are, summaries to the list...

A. When you call fopen(), be sure to set the second parameter to "rb",
   "wb", or whatever.  Just make sure there is a "b" in there.  This
   will also work on UNIX without modification.  For example:

	fopen("binary.fil", "rb");

B. When you call open(), binary-or O_BINARY into the second parameter.
   If the code will also be used on UNIX, it is common to define
   O_BINARY if it does not already exist.  For example:

	#include <fcntl.h>

	#ifndef	O_BINARY
	#define	O_BINARY	0
	#endif

	open("binary.fil", O_RDONLY | O_BINARY);

C. By default, stdin, stdout, and stderr are in text mode.  You need
   to call setmode() to fix them.  As I recall, you need to include
   <fcntl.h> to get O_BINARY.  If the code is to be used on UNIX, you
   should surround this with "#ifdef __MSDOS__".  For example:

	#include <fcntl.h>

	#ifdef	__MSDOS__
	    setmode(fileno(stdin), O_BINARY);
	    setmode(fileno(stdout), O_BINARY);
	#endif

D. If you switch a file between text and binary or binary and text
   mode, and you are using stdio on that file, you should flush the
   buffers to that file before switching.

If you follow these rules, everything should work fine.
--
				Eric Backus
				ericb AT lsid DOT hp DOT com
				(206) 335-2495

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