MATLAB Answers

Hugo SP

textscan to parse string

Asked by Hugo SP
on 20 Feb 2013


I am trying to use textscan to parse an IP address to get 4 integers:

str = ''

integers = textscan(str,'%u8',4, 'Delimiter', '.');

Why is this is not working correctly?

Thank you.




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1 Answer

Answer by Walter Roberson
on 20 Feb 2013
 Accepted answer

Unfortunately, in at least some versions, textscan() keeps reading for numeric fields as long as what is in the input is characters that could be part of a number format. It does not pay attention to the delimiter until after it has done that.

So the is read as "4 is a digit, 8 is a digit, decimal place is part of a floating point format, 2 is a digit, decimal point has already occurred in the number so the number must have ended, 48.2; now look, the decimal point is the delimiter. Okay 8 and 1 are digits, decimal point is part of a floating point format, 5 and 6 are digits, end of string so the number has ended, 81.56. Now convert the 48.2 and 81.56 into the %u8 format."

What you should do instead is

integers = uint8( str2double( regexp( str, '\.', 'split' ) ) )


Yes, that is an alternative to 'split'; the str2double() and uint8() would still be needed around it, of course.

Hugo SP
on 20 Feb 2013

Thank you for the answer. However, I think that this is a bug and should be corrected. I don't understand how '.' is part of an integer format, which is what I requested. If it was %f I would understand the error.

Please submit a bug report; I do not work for Mathworks.

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