juergen perlinger, posting in the Usenet group comp.std.c, points out an apparent error in the scanf(3) man page. The same error exists in the online version at http://www.kernel.org/doc/man-pages/online/pages/man3/scanf.3.html The discussion can be seen via https://groups.google.com/d/topic/comp.std.c/j5g9-orzPc8/discussion Here's the relevant portion of the man page: n Nothing is expected; instead, the number of characters consumed thus far from the input is stored through the next pointer, which must be a pointer to int. This is not a conversion, although it can be suppressed with the * assignment-suppression character. The C standard says: "Execution of a %n directive does not increment the assignment count returned at the completion of execution" but the Corrigendum seems to contradict this. Probably it is wise not to make any assumptions on the effect of %n conversions on the return value. Here's the text from the C99 standard, quoted from http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf which includes the C99 standard with all three Technical Corrigenda. Changes are marked with change bars; there are none in this section. n No input is consumed. The corresponding argument shall be a pointer to signed integer into which is to be written the number of characters read from the input stream so far by this call to the fscanf function. Execution of a %n directive does not increment the assignment count returned at the completion of execution of the fscanf function. No argument is converted, but one is consumed. If the conversion specification includes an assignment-suppressing character or a field width, the behavior is undefined. The man page's statement that "it can be suppressed with the * assignment-suppression character" may be incorrect, or it may just be glibc-specific (an implementation may define the behavior of something whose behavior is left undefined by the standard); if the latter, it would be useful to mention this. I see nothing in any Corrigendum that supports the last two sentences of the quoted paragraph in the man page. (There's also nothing relevant in the 1995 amendment to the C90 standard.) As far as I can tell, it's simply wrong. -- Keith Thompson (The_Other_Keith) kst@xxxxxxx <http://www.ghoti.net/~kst> Nokia "We must do something. This is something. Therefore, we must do this." -- Antony Jay and Jonathan Lynn, "Yes Minister" -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
