Newsgroups:	comp.programming,comp.os.msdos.djgpp
From:	smryan AT netcom DOT com (!@?*$%)
Subject:	Re: standard input and files
Message-ID:	<smryan-1310961125290001@10.0.2.15>
Sender:	smryan AT netcom3 DOT netcom DOT com
Organization:	The Programmer formerly known as S M Ryan
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 961013125209 DOT 5008A-100000 AT sun4 DOT iol DOT unh DOT edu>
Date:	Sun, 13 Oct 1996 19:23:23 GMT
Lines:	23
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

> from standard input or from a file.  Like the more command ( on unix ) or 
> grep or something.  I also want to use ifstreams to do the input.  

As a side note, more uses two input files, stdin and the controlling
terminal of the session.

>         Can I assume that standard input is always file descriptor 0, or 

Yes. (stdio makes the same assumption.) In Unix, if descriptor 0 is open
then whatever file it is, it is standard input. Descriptor 1 is always
stdout, descriptor 2 is always stderr.

The descriptors aren't sacred: you close them and open some other file
there if you want, but every shell guarentees 0, 1, and 2 are open, 0 is
readable, 1 and 2 are writable. It is possible that if your program is
execed from a non-shell, descriptor 0 could be closed or not readable, but
that would then be a violation of your program's calling conventions.

-- 
The winter ceased its weary grip    | smryan AT netcom DOT com  PO Box 1563
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