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From: mark@cbosgd.UUCP (Mark Horton)
Newsgroups: net.lang.c,net.unix-wizards,net.wanted
Subject: Re: need info: %r in printf
Message-ID: <436@cbosgd.UUCP>
Date: Fri, 14-Oct-83 15:17:52 EDT
Article-I.D.: cbosgd.436
Posted: Fri Oct 14 15:17:52 1983
Date-Received: Sun, 16-Oct-83 11:00:49 EDT
References: <164@washu.UUCP>
Organization: AT&T Bell Laboratories, Columbus
Lines: 23

I think %r was in UNIX/32V (undocumented) and possibly V7.
It went away in 4BSD and was never in System III or its
precursors.

Calling _doprnt is very unportable.  In particular, System III
and V don't have _doprnt, they have _print, with slightly
different conventions.  There are also slight differences
between V7 and 32V.

The next release of System V has something called vsprintf:
	vsprintf(string, format, ap)
	char *string, *fmt;
	va_list ap;
(see varargs(3)).  This is like sprintf, except that ap is
something that can be passed through more than one layer of
function (e.g. it's normally a pointer to the first argument
in the list.) Assuming you consider System V "standard",
this will be the first documented way to do this in "standard UNIX".

In general, this is useful when you want to provide a printf-style
routine for other routines to use.  It's great for debugging and
error messages.  It's also useful when you want to provide a
subroutine package - e.g. printw in curses.