sscanf read error

This is a discussion on sscanf read error within the C Programming forums, part of the General Programming Boards category; The man page of 'sscanf' says: "EOF is also returned if a read error occurs, in which case the error ...

  1. #1
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    sscanf read error

    The man page of 'sscanf' says:

    "EOF is also returned if a read error occurs, in which case the error indicator for the stream (see ferror(3)) is set, and errno is set indicate the error"

    I am confused that what kind of read error may occur if sscanf is reading from a buffer on stack???

  2. #2
    and the hat of wrongness Salem's Avatar
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    An empty string perhaps?
    Try some tests for yourself?
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    ok, Let me elaborate, i have a text file that contains lines like:

    ABCD 6 0
    EFGH 1 0

    and so on.....

    what i do is, i read each line using 'fgets()' in a char buffer say read_buff, apply a regular expression over it, that ensures the presence of two integers after the name, now by using sscanf i am reading the integers into integer variables, my question is that should i handle the read error specified in man pages, if yes, then please tell me the scenario in which it may occur....

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    CSharpener vart's Avatar
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    Quote Originally Posted by me_ansh View Post
    ok, Let me elaborate, i have a text file that contains lines like:

    ABCD 6 0
    EFGH 1 0

    and so on.....

    what i do is, i read each line using 'fgets()' in a char buffer say read_buff, apply a regular expression over it, that ensures the presence of two integers after the name, now by using sscanf i am reading the integers into integer variables, my question is that should i handle the read error specified in man pages, if yes, then please tell me the scenario in which it may occur....
    you should check the return value of sscanf

    if it is less than number of items to be formatted - do something (probably ignore the line)

    so for you return value of -1 should not be different from return value of 0
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    Ya, that is what i am asking...if i have ensured by my regular expression that integers are present, then is there a possiblity that sscanf may return error??, if yes, then is there a specific case that u may highlight ??

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    CSharpener vart's Avatar
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    Quote Originally Posted by me_ansh View Post
    Ya, that is what i am asking...if i have ensured by my regular expression that integers are present, then is there a possiblity that sscanf may return error??, if yes, then is there a specific case that u may highlight ??
    Couldn't say without seeing the regular expression and sscanf format used

    PS. And I do not see a reason for using regular expressions while you could simply check the return value of sscanf (and maybe the first unparsed char if you interrested to known if really all the string was parsed)
    Last edited by vart; 01-28-2009 at 02:33 AM.
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    I suspect that in the case of sscanf(), it's UNLIKELY that EOF is returned, but some systems may be able to detect situations where it want's to give an error message back (e.g. validating the string storage and finding it invalid in some way).

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