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Internet Message Format | 1996-08-05 | 3.5 KB

Path: newshost.lanl.gov!tanmoy
From: [e-mail] (Tanmoy Bhattacharya)
Newsgroups: comp.lang.c
Subject: Re: Explain this> %s \"%[^\"]\"
Date: 29 Feb 1996 16:59:03 GMT
Organization: Los Alamos National Laboratory
Distribution: world
Message-ID: <[e-mail]>
References: <4h2t6u$[e-mail]>
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Content-Type: text
In-reply-to: [e-mail]'s message of 29 Feb 1996 00:49:34 GMT

In article <4h2t6u$[e-mail]>
[e-mail] (David Cunningham) writes:
<snip>
DC:
DC: I have a file that contains text like this:
DC:
DC: 012345678     "Joe  Smith"
DC:
DC:
DC: I also have an example of sscanf to pick out these fields. Can someone
DC: translate what  \"%[^\"]\"%d"  means. I need to have a good understanding

Nothing. It is not even a complete token :-)

DC: of this for a homework assignment. It looks like this:
DC:
DC: sscanf(buff,"%s \ "%[^\"]\" %d",student_list->ss_num,student_list->name);

Nothing. lexical error again. (And if the lexical error were
corrected, there would have been a programming error: you are telling
scanf to fill three locations and passing it only two things: I am not
even sure they have the right type. WHY do people not post a _short_
complete compilable example: Steve, can the posted copy of the FAQ
mention it in large bold letters: THOU SHALT NOT LITTER C.L.C. WITH
ANY FRAGMENT THAT SPEWETH OFF YOUR FINGERS? A lot more bandwidth is
wasted by improper discussions than by people actually posting code).

If you need to understand the hieroglyphics, first you have to learn
to reproduce them :-)

Anyway, "%[^\"]\"%d" is a string literal, that is an unmodifiable
static array of characters containing the following chars:
'%','[','^','"',']','"','%','d' and '\0'. When sent to scanf it
encodes the following instructions:

1) Match (%) the sequence of any characters ([...]) that do not (^)
   contain '"'; and put the result in whatever the first following
   argument points to. Assume that the argument is a pointer to char.
   (If no such character exists, stop).
2) Check that the next character is a '"'. If it is not stop. If so,
   discard it.
3) Read an integer after skipping over whitespace, and store it in
   whatever the next argument points to. Assume that argument is a
   pointer to int.
   (If an integer is not found, stop)

Return the number of things stored.

"%s \"%[^\"]\" %d" means (in less detail than above):

1) Means read a sequence of non-whitespace characters and store it in
   the pointer to char passed.
2) skip over whitespace
3) check and read a following ".
4) Read non-" characters and store them in a pointer to char that
   follows.
5) check and read a following ".
6) skip over blanks.
7) skip over blanks and read a decimal integer storing it in the
   pointer to int provided.

Hope this helps

<snip>
DC: Please explain what these hieroglyphics mean, character by character.
DC:
DC: The sscanf will produce this--> 012345678  Joe Smith
DC:

I do not know any sense in which a sscanf shall produce
anything. Could you explain?

Cheers
Tanmoy
--
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