sscanf

This is a discussion on sscanf within the C Programming forums, part of the General Programming Boards category; I have following code snap written in VC++ 6.0 if ( sscanf( p,"%02x",&ID ) != 1 ) { printf("ID = ...

  1. #1
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    Feb 2003
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    sscanf

    I have following code snap written in VC++ 6.0
    if ( sscanf( p,"%02x",&ID ) != 1 )
    {
    printf("ID = %d\n",ID);
    return Error;
    }

    If p = “tt” or “TZ” or “Za” or “R5” it returns error but “4T” or “7G” does not.

    What change do I need to make to return error even for “4T” and “7G”?

    That is, I want to return error if any of the character is non-numeric.

  2. #2
    ATH0 quzah's Avatar
    Join Date
    Oct 2001
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    14,826
    Don't use sscanf. You cannot force it to read 2 bytes always. You should just do it manually.

    Read one byte. Check for 0-9 or a-f. If it isn't, throw an error. If it is, read another byte and check it.

    You're misunderstanding how the *scanf functions work. They read until they don't find something that is readable. Then they put that item back onto the stream, so it counts as not being read.

    So, they see that 4 or 7 is valid, so they use it. They see that T or G is invalid, so they say, well, we've found one item. Push the T or G back, and return that we've found one usable item...

    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
    End Of Line Hammer's Avatar
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    strtol() : You can use this with error checking quite easily.
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

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