The c-strcasecmp module contains a case-insensitive string comparison
function operating on single-byte character strings, like the functions in
<strings.h>, that operate as if the locale encoding was ASCII.
(The "C" locale on many systems has the locale encoding "ASCII".)
The function is:
extern int c_strcasecmp (const char *s1, const char *s2);
For case conversion here, only ASCII characters are considered to be upper case or lower case.
Note: The function strcasecmp from <strings.h>
supports only unibyte locales;
for multibyte locales,
you need the function mbscasecmp.