16.1.4.4 c-strcasestr

The c-strcasestr module contains a case-insensitive string search function operating on single-byte character strings, that operate as if the locale encoding was ASCII. (The "C" locale on many systems has the locale encoding "ASCII".)

The function is:

extern char *c_strcasestr (const char *haystack, const char *needle);

For case conversion here, only ASCII characters are considered to be upper case or lower case.

Note: The function strcasestr from <string.h> supports only unibyte locales; for multibyte locales, you need the function mbscasestr.