sscanf won't *require* a space

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D Kaden

• March 01, 2018 12:14

I want to scan text input for a command followed by hexadecimal numbers.  My format string has a space separating the word and the %x, but sscanf won't require it.  If the word ends with [abcdef], sscanf takes that as a hexadecimal number instead of part of the word.

For example, here's the format string:  "en %X %X".  If the input text is "en 3 4", it works as expected, but if the input is "enc 3 4", sscanf sees that as the word "en" followed by the hex number "c".  I want it to not match because "enc" != "en".  Since the space after "en" in the format string was ignored, I set "Scanf Classes Supported" = yes and tried many variations of explicitly specifying that I require a space there ("%[ ]", "%*[]", "%*[ \t]"), but nothing works.  (But they do work in Visual C++.)

sscanf("en 3 4", "en %X %X", &x, &y);    // x=3, y=4.  OK.
sscanf("enc 3 4", "en %X %X", &x, &y);   // x=12, y=3.  Not OK.
sscanf("enc 3 4", "en%*[ ]%X %X", &x &y);// Same result: x=12, y=3.

How do I get sscanf to require a space where I've specified?

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  Jon Elliott

  • March 01, 2018 14:20

  I get exactly the same behaviour using Visual Studio 2015 and Linux GCC.

  Perhaps it would be better to do something like:

  if (sscanf("en 3 4", "%s %X %X", str, &x, &y) == 3 && strcmp(str, "en") == 0)
    ..

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