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| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: sscanf error checking |
| Date | 2016-12-14 19:49 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <871sxa70kq.fsf@bsb.me.uk> (permalink) |
| References | <o2rp71$3e7$1@dont-email.me> <o2rqur$5t5$1@news.xmission.com> <o2s0o1$fb$1@dont-email.me> |
BartC <bc@freeuk.com> writes:
> On 14/12/2016 16:11, Kenny McCormack wrote:
>> In article <o2rp71$3e7$1@dont-email.me>, BartC <bc@freeuk.com> wrote:
>> ...
>>> Output:
>>>
>>> Status = 1
>>> X = 123.000000
>>>
>>> The same when scanning "123GARBAGE". It's just stopping when it sees
>>> something that can't be part of the number without reporting anything
>>> amiss. Which is not far off why I do.
>>>
>>> Am I doing something wrong or is sscanf not as great at verifying input
>>> as is made out?
>
>> You're supposed to use %n to verify that it scanned everything it was
>> supposed to scan.
>>
>> I changed your program to:
>>
>> #include <stdio.h>
>> #include <string.h>
>>
>> int main(void)
>> {
>> double x;
>> int status,n;
>> char* str = "123..456";
>>
>> status = sscanf(str,"%lf%n",&x,&n);
>>
>> printf("Status = %d, n = %d, length = %lu\n",status,n,strlen(str));
>> printf("X = %f\n",x);
>> }
>>
>> And you can see that the value of 'n' and the length of the string are not equal.
>> That indicates that something went wrong.
>
> OK, thanks.
(It's slightly simpler to test that str[n] is 0.)
<snip>
> (Actually, up to now I've only used sscanf in one place and that /was/
> with a "%lf%n" format, but that was to be able to step to the next
> item within a larger string.)
The code that (I thought) you wrote for your line input exercise has
sscanf(s,"%lf",&x) in the strtofloat function.
--
Ben.
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
sscanf error checking BartC <bc@freeuk.com> - 2016-12-14 15:42 +0000
Re: sscanf error checking John Gordon <gordon@panix.com> - 2016-12-14 15:58 +0000
Re: sscanf error checking Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2016-12-14 11:14 -0500
Re: sscanf error checking gazelle@shell.xmission.com (Kenny McCormack) - 2016-12-14 16:11 +0000
Re: sscanf error checking BartC <bc@freeuk.com> - 2016-12-14 17:51 +0000
Re: sscanf error checking gazelle@shell.xmission.com (Kenny McCormack) - 2016-12-14 18:09 +0000
Re: sscanf error checking Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-14 19:49 +0000
Re: sscanf error checking BartC <bc@freeuk.com> - 2016-12-14 20:43 +0000
Re: sscanf error checking Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-14 16:40 +0000
Re: sscanf error checking Keith Thompson <kst-u@mib.org> - 2016-12-14 09:34 -0800
Re: sscanf error checking Robert Wessel <robertwessel2@yahoo.com> - 2016-12-14 14:52 -0600
Re: sscanf error checking supercat@casperkitty.com - 2016-12-15 07:24 -0800
Re: sscanf error checking Keith Thompson <kst-u@mib.org> - 2016-12-15 11:26 -0800
Re: sscanf error checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-12-15 15:35 -0800
Re: sscanf error checking Keith Thompson <kst-u@mib.org> - 2016-12-15 16:28 -0800
Re: sscanf error checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-12-15 16:37 -0800
Re: sscanf error checking supercat@casperkitty.com - 2016-12-15 16:38 -0800
Re: sscanf error checking raltbos@xs4all.nl (Richard Bos) - 2016-12-15 20:20 +0000
Re: sscanf error checking Keith Thompson <kst-u@mib.org> - 2016-12-15 12:33 -0800
sscanf error checking asetofsymbols@gmail.com - 2016-12-16 01:49 -0800
sscanf error checking asetofsymbols@gmail.com - 2016-12-16 01:53 -0800
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