sscanf

**Allan Bruce** · Nov 14 '05, 05:55 AM

Re: sscanf

"Allan Bruce" <allanmb@TAKEAW AYf2s.com> wrote in message
news:c5o8ge$a8j $1@news.freedom 2surf.net...[color=blue]
> If I have
> sscanf("FL:%s:% d:%s\n", lGuid, &lID, lFileName);
>
> and the last string contains spaces, e.g. my complete string
> "FL:1234ABCD:3: FileName With Spaces.txt\n"
>
> does sscanf just make lFileName the string up to the whitespace? even[/color]
though[color=blue]
> I tell it the end of string as at the \n ?
>
> Thanks
> Allan
>
>[/color]

also, is there a way to set ':' as a terminator for the string? I jsut
realised that my lGuid will continue until the next whitespace or \0
Thanks
Allan

**Irrwahn Grausewitz** · Nov 14 '05, 05:55 AM

Re: sscanf

"Allan Bruce" <allanmb@TAKEAW AYf2s.com> wrote:[color=blue]
>
>"Allan Bruce" <allanmb@TAKEAW AYf2s.com> wrote:[color=green]
>> If I have
>> sscanf("FL:%s:% d:%s\n", lGuid, &lID, lFileName);[/color][/color]
^
You forgot to specify the string to parse
[color=blue][color=green]
>> and the last string contains spaces, e.g. my complete string
>> "FL:1234ABCD:3: FileName With Spaces.txt\n"
>>
>> does sscanf just make lFileName the string up to the whitespace? even[/color]
>though[color=green]
>> I tell it the end of string as at the \n ?[/color]
>
>also, is there a way to set ':' as a terminator for the string? I jsut
>realised that my lGuid will continue until the next whitespace or \0[/color]

Warning, untested:

sscanf( yourstring, "FL:%[^:]:%d:%[^\n]\n", lGuid, &lID, lFileName);

If the ':'s might be surrounded by whitespace that should be ignored,
you'll have to match and discard that, too.

HTH
Regards
--
Irrwahn Grausewitz (irrwahn33@free net.de)
welcome to clc: http://www.ungerhu.com/jxh/clc.welcome.txt
clc faq-list : http://www.faqs.org/faqs/C-faq/faq/
clc OT guide : http://benpfaff.org/writings/clc/off-topic.html

**Allan Bruce** · Nov 14 '05, 05:56 AM

Re: sscanf

>[color=blue]
> Warning, untested:
>
> sscanf( yourstring, "FL:%[^:]:%d:%[^\n]\n", lGuid, &lID, lFileName);
>
> If the ':'s might be surrounded by whitespace that should be ignored,
> you'll have to match and discard that, too.
>
> HTH
> Regards[/color]

I tried:
sscanf(xiBuffer , "FL:%d:%[^:]s:%d:%[^\n]s\n", &lID, lGUID, &lFileLength ,
lFileName);

the lGUID gets read fine, but nothing after this gets read. Where can I
find information about these scan types?
Thanks
Allan

**Irrwahn Grausewitz** · Nov 14 '05, 05:56 AM

Re: sscanf

"Allan Bruce" <allanmb@TAKEAW AYf2s.com> wrote:[color=blue][color=green]
>>
>> Warning, untested:
>>
>> sscanf( yourstring, "FL:%[^:]:%d:%[^\n]\n", lGuid, &lID, lFileName);
>>
>> If the ':'s might be surrounded by whitespace that should be ignored,
>> you'll have to match and discard that, too.
>>
>> HTH
>> Regards[/color]
>
>I tried:
>sscanf(xiBuffe r, "FL:%d:%[^:]s:%d:%[^\n]s\n", [....][/color]
^ ^
You've got two spurious s characters at the indicated positions.
[color=blue]
>the lGUID gets read fine, but nothing after this gets read. Where can I
>find information about these scan types?[/color]

Hm, RTFM? ;-)
Seriously, your implementation should provide a documentation of the
standard library functions. Alternatively, buy the C standard, or,
if you're short on money, retrieve a copy of the final public draft
for free at: http://anubis.dkuug.dk/jtc1/sc22/wg14/www/docs/n869/ .

As a starter, here's an excerpt from the *scanf function description:

ISO/IEC 9899:1999
7.19.6.2 The fscanf function
[...]

[ Matches a nonempty sequence of characters from a set of expected
characters (the scanset). If no l length modifier is present, the
corresponding argument shall be a pointer to the initial element of
a character array large enough to accept the sequence and a
terminating null character, which will be added automatically.
[...] The conversion specifier includes all subsequent characters
in the format string, up to and including the matching right
bracket (]). The characters between the brackets (the scanlist)
compose the scanset, unless the character after the left bracket is
a circumflex (^), in which case the scanset contains all characters
that do not appear in the scanlist between the circumflex and the
right bracket. [...]

HTH
Regards
--
Irrwahn Grausewitz (irrwahn33@free net.de)
welcome to clc: http://www.ungerhu.com/jxh/clc.welcome.txt
clc faq-list : http://www.faqs.org/faqs/C-faq/faq/
clc OT guide : http://benpfaff.org/writings/clc/off-topic.html

**Allan Bruce** · Nov 14 '05, 05:56 AM

Re: sscanf

[color=blue][color=green]
> >I tried:
> >sscanf(xiBuffe r, "FL:%d:%[^:]s:%d:%[^\n]s\n", [....][/color]
> ^ ^
> You've got two spurious s characters at the indicated positions.
>[color=green]
> >the lGUID gets read fine, but nothing after this gets read. Where can I
> >find information about these scan types?[/color]
>
> Hm, RTFM? ;-)
> Seriously, your implementation should provide a documentation of the
> standard library functions. Alternatively, buy the C standard, or,
> if you're short on money, retrieve a copy of the final public draft
> for free at: http://anubis.dkuug.dk/jtc1/sc22/wg14/www/docs/n869/ .
>
>[/color]

Thanks, I have it working now.
Allan

**Dan Pop** · Nov 14 '05, 05:56 AM

Re: sscanf

In <c5o8ge$a8j$1@n ews.freedom2sur f.net> "Allan Bruce" <allanmb@TAKEAW AYf2s.com> writes:
[color=blue]
>If I have
>sscanf("FL:%s: %d:%s\n", lGuid, &lID, lFileName);[/color]

You're invoking undefined behaviour, because the input string is missing
from your sscanf call.
[color=blue]
>and the last string contains spaces, e.g. my complete string
>"FL:1234ABCD:3 :FileName With Spaces.txt\n"
>
>does sscanf just make lFileName the string up to the whitespace?[/color]

Yup.
[color=blue]
>even though I tell it the end of string as at the \n ?[/color]

Nope, you're not telling it anything like that. You're merely telling
it to eat *any* whitespace it finds after the string (which is a noop in
your case, since you're using sscanf and not [f]scanf). There is NO way
to tell %s that the first white space encountered is not ending the input
string. You have to use a more sophisticated conversion descriptor for
this purpose:

#define INPUT "FL:1234ABCD:3: FileName With Spaces.txt\n"

int rc = sscanf(INPUT, "FL:%s:%d:%[^\n]", lGuid, &lID, lFileName);

Things to remember:

1. If lFileName is not large enough to hold the whole first argument of
the sscanf call, use an explicit maximum input field specification; no
need to rediscover the joys of gets. This also applies to %s.

2. Unlike most conversion specifications, including %s, %[ doesn't skip
any preceding white space (just like %c). If needed, use an explicit
white space in the format string, for this purpose (it is harmless if
there is no white space at all at that point in the input string).

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Dan Pop** · Nov 14 '05, 05:56 AM

Re: sscanf

In <c5om52$raf$15@ sunnews.cern.ch > I wrote:
[color=blue]
>In <c5o8ge$a8j$1@n ews.freedom2sur f.net> "Allan Bruce" <allanmb@TAKEAW AYf2s.com> writes:
>[color=green]
>>If I have
>>sscanf("FL:%s :%d:%s\n", lGuid, &lID, lFileName);[/color]
>
>You're invoking undefined behaviour, because the input string is missing
>from your sscanf call.
>[color=green]
>>and the last string contains spaces, e.g. my complete string
>>"FL:1234ABCD: 3:FileName With Spaces.txt\n"
>>
>>does sscanf just make lFileName the string up to the whitespace?[/color]
>
>Yup.
>[color=green]
>>even though I tell it the end of string as at the \n ?[/color]
>
>Nope, you're not telling it anything like that. You're merely telling
>it to eat *any* whitespace it finds after the string (which is a noop in
>your case, since you're using sscanf and not [f]scanf). There is NO way
>to tell %s that the first white space encountered is not ending the input
>string. You have to use a more sophisticated conversion descriptor for
>this purpose:
>
> #define INPUT "FL:1234ABCD:3: FileName With Spaces.txt\n"
>
> int rc = sscanf(INPUT, "FL:%s:%d:%[^\n]", lGuid, &lID, lFileName);[/color]

Which is plagued by the problem already mentioned downthread by Allan:
%s will eat too much, stopping after FileName. So, %s is not the right
thing for lGuid, either:

int rc = sscanf(INPUT, "FL:%[^:]:%d:%[^\n]", lGuid, &lID, lFileName);

NEVER omit to check rc, to see if all the fields have been properly
converted.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Bill Cunningham** · Nov 14 '05, 06:00 AM

Re: sscanf

[color=blue][color=green]
> > If I have
> > sscanf("FL:%s:% d:%s\n", lGuid, &lID, lFileName);[/color][/color]
^

That's a C++ reference operator isn't it? I don't think that has
anything to do with a pointer. It is a COM Interface ID isn't it?

Bill

**Bill Cunningham** · Nov 14 '05, 06:00 AM

Re: sscanf

> the lGUID gets read fine, but nothing after this gets read. Where can I[color=blue]
> find information about these scan types?
> Thanks
> Allan
>[/color]
sscanf reads a string instead of input from a keyboard.

http://www-ccs.ucsd.edu/c/

Bill

**Allan Bruce** · Nov 14 '05, 06:00 AM

Re: sscanf

"Bill Cunningham" <nospam@nspam.n et> wrote in message
news:1085dtb3k0 9hl8f@corp.supe rnews.com...[color=blue]
>[color=green][color=darkred]
> > > If I have
> > > sscanf("FL:%s:% d:%s\n", lGuid, &lID, lFileName);[/color][/color]
> ^
>
> That's a C++ reference operator isn't it? I don't think that has
> anything to do with a pointer. It is a COM Interface ID isn't it?
>
> Bill
>
>[/color]

no, sscanf requires a pointer to write to, this is just an integer declared
the line above as :
int lID;
so the & is taking the address of it to make a pointer on the fly.
Allan

**Bill Cunningham** · Nov 14 '05, 06:00 AM

Re: sscanf

> no, sscanf requires a pointer to write to, this is just an integer
declared[color=blue]
> the line above as :
> int lID;
> so the & is taking the address of it to make a pointer on the fly.
> Allan
>[/color]
Oh I see. that IID just looked like an interface identifier.

Bill

sscanf

sscanf

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