Date: Tue, 23 Jan 2007 08:59:12 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-standards@FreeBSD.ORG, giecrilj@stegny.2a.pl Subject: Re: return value of fprintf Message-ID: <200701230759.l0N7xCdg002571@lurza.secnetix.de> In-Reply-To: <005301c73e6c$ba6ffd00$1a01080a@POCZTOWIEC>
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K?i?tof ?elechovski <giecrilj@stegny.2a.pl> wrote: > The > <http://www.freebsd.org/cgi/man.cgi?query=fprintf&apropos=0&sektion=0&manpat > h=FreeBSD+7-current&format=html> fprintf manual page says it is ANSI C > compatible and it returns the number of characters printed. > > The latter is correct: I get printf("abcd") == 4 even under >/dev/full. > (uname is Interix on x86 ver. 3.5) Because the printf() function doesn't write to /dev/full directly. It writes to a stdio buffer associated with the standard output stream. > However, the former is not: according to the ANSI C standard > <http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1124.pdf>; , §7.19.6.1/14, > printf should return a negative value in this case. POSIX/SUSv4 (which is aligned with the ISO C standard) says: "If an output error was encountered, these functions shall return a negative value." FreeBSD is compliant with that specification. Note the use of the words "if ... encountered": If the file system is full, that condition is encountered _only_ the next time the stdio library flushes its buffer (which can be as late as the close() call). It is _not_ encountered by the fprintf() function itself, so it is perferctly legal that it does not return a negative value. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "Emacs ist für mich kein Editor. Für mich ist das genau das gleiche, als wenn ich nach einem Fahrrad (für die Sonntagbrötchen) frage und einen pangalaktischen Raumkreuzer mit 10 km Gesamtlänge bekomme. Ich weiß nicht, was ich damit soll." -- Frank Klemm, de.comp.os.unix.discussion
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