Date: Fri, 05 Jan 2001 17:29:42 +0000 From: Brian Somers <brian@Awfulhak.org> To: Ben Smithurst <ben@FreeBSD.org> Cc: Brian Somers <brian@Awfulhak.org>, Chris Faulhaber <jedgar@fxp.org>, Will Andrews <will@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org, brian@Awfulhak.org Subject: Re: cvs commit: src/usr.bin/apply apply.c Message-ID: <200101051729.f05HTgi47555@hak.lan.Awfulhak.org> In-Reply-To: Message from Ben Smithurst <ben@FreeBSD.org> of "Fri, 05 Jan 2001 16:29:17 GMT." <20010105162917.K85794@strontium.scientia.demon.co.uk>
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> Brian Somers wrote:
>
> > Also (and this bug was already there), s[n]printf() returns the length
> > of what it would have liked to have put in the target, not what it
> > actually wrote. If the first s[n]printf() above ends up truncating,
> > the second one will happily overflow.
>
> Well, with sprintf, there is no difference, since it doesn't have a size
> limitation like snprintf does.
>
> > s[n]printf() is poorly documented in this area.
>
> Would this change make you feel better?
>
> change this:
>
> Snprintf() and vsnprintf() will write at most size-1 of the characters
> printed into the output string (the size'th character then gets the ter-
> minating `\0'); if the return value is greater than or equal to the size
> argument, the string was too short and some of the printed characters
> were discarded.
>
> to this:
>
> Snprintf() and vsnprintf() will write at most size-1 of the characters
> printed into the output string (the size'th character then gets the ter-
> minating `\0'), and return the number of characters written to the
> buffer, excluding the terminating `\0'. This value may be less than the
> number of characters which would have been written, had the buffer been
> large enough; if the return value is greater than or equal to the size
> argument, the string was too short and some of the printed characters
> were discarded.
I guess this proves my point about the documentation being inadequate
:-). The return value is the amount that would have been written had
there been enough space, *not* the amount that was actually written.
hak:~ $ cat x.c
#include <stdio.h>
int
main(int argc, char **argv)
{
char x[5];
int n;
n = snprintf(x, sizeof x, "hello world");
printf("Got \"%s\", %d\n", x, n);
return 0;
}
hak:~ $ cc -o x x.c
hak:~ $ ./x
Got "hell", 11
> --
> Ben Smithurst / ben@FreeBSD.org / PGP: 0x99392F7D
--
Brian <brian@Awfulhak.org> <brian@[uk.]FreeBSD.org>
<http://www.Awfulhak.org>; <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !
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