sscanf error checking

From	BartC <bc@freeuk.com>
Newsgroups	comp.lang.c
Subject	sscanf error checking
Date	2016-12-14 15:42 +0000
Organization	A noiseless patient Spider
Message-ID	<o2rp71$3e7$1@dont-email.me> (permalink)

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I got the impression, according to the 'while-loop reading from file' 
thread (where I was strongly chastised for being lax with 
error-handling), that 'sscanf' was /the/ way to detect errors in 
numerical input.

But then I come across this:

   double x;
   int status;
   char* str = "123..456";

   status = sscanf(str,"%lf",&x);

   printf("Status = %d\n",status);
   printf("X      = %f\n",x);

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?

Doing strtof("123..456",0) returns 123.0000.

If I do float("123..456") in Python it reports an error.

-- 
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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