Case Insensitive String comp in C

c string standard-library
bond425 picture bond425 · Apr 28, 2011 · Viewed 167.6k times · Source

I have two postcodes char* that I want to compare, ignoring case. Is there a function to do this?

Or do I have to loop through each use the tolower function and then do the comparison?

Any idea how this function will react with numbers in the string

Thanks

Answer

Fred Foo picture Fred Foo · Apr 28, 2011

There is no function that does this in the C standard. Unix systems that comply with POSIX are required to have strcasecmp in the header strings.h; Microsoft systems have stricmp. To be on the portable side, write your own:

int strcicmp(char const *a, char const *b)
{
    for (;; a++, b++) {
        int d = tolower((unsigned char)*a) - tolower((unsigned char)*b);
        if (d != 0 || !*a)
            return d;
    }
}

But note that none of these solutions will work with UTF-8 strings, only ASCII ones.

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