Xref: utzoo comp.lang.c:17040 comp.unix.wizards:15106
Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!tut.cis.ohio-state.edu!rutgers!cmcl2!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn )
Newsgroups: comp.lang.c,comp.unix.wizards
Subject: Re: How to predict size of outcome of vsprintf?
Keywords: vsprintf formatted conversion
Message-ID: <9872@smoke.BRL.MIL>
Date: 19 Mar 89 05:52:35 GMT
References: <993@etnibsd.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 17

In article <993@etnibsd.UUCP> sean@etnibsd.UUCP (Sean McElroy) writes:
>O.K. Unix/C gurus, since vsprintf requires the user to ensure that there
>is enough space in the output string, how does one predict the size of
>the output string?  Is there a routine which returns the predicted
>length of the output string (effectively preforming the printf conversions)
>without actually producing the output string?

No.  Sometimes you can accurately predict an upper bound on the output
string length; for example if the format is "%d" and the numerical
argument is known to lie between 0 and 5000, the maximum number of
characters for the *sprintf() output will be 5 (including the null
byte at the end).

>Any suggestions welcome.

Don't use *sprintf() when you can't be sure that the output length
will be small enough.  Seriously.