Parse data from input string

Question

I'm having this kind of input data.

<html>...... 

I only want to extract the data before the comment sign <!--. This is my code:

char *parse_data(char *input) {
    char *parsed_data = malloc(strlen(input) * sizeof(char));
    sscanf(input, "%s<!--%*s", parsed_data);
    return parsed_data;
}

However, it doesn't seem to return the expected result. I can't figure out why is that so.

Could anyone explain me the proper way to extract this kind of data and the behavior of 'sscanf()`.

Thank you!

hmjd · Accepted Answer · 2012-11-09 09:29:21Z

4

The "%s" format specifier will not treat "<!--" as a single delimiter, or any of the individual characters as a delimiter (which would not be the correct behaviour anyway). Only whitespace is considered a delimiter. Scan sets are available in sscanf() but they take a collection of individual characters rather that a sequence of characters representing a single delimiter. This means that everything in input before the first whitespace character will be assigned to parsed_data.

You could use strstr() instead:

const char* comment_start = strstr(input, "<!--");
char* result = 0;
if (comment_start)
{
    result = malloc(comment_start - input + 1);
    memcpy(result, input, comment_start - input);
    result[comment_start - input] = 0;
}

Note that sizeof(char) is guaranteed to be 1 so can be omitted as part of the malloc() argument calculation.

edited Nov 9, 2012 at 9:29

answered Nov 9, 2012 at 9:22

hmjd

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