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Re: sscanf error checking

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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. I'll be using sscanf on a string that already contains a 
trimmed, single item that either ought to contain only a number, or that 
I'm checking contains only a number.

(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.)

-- 
Bartc

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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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