/* * strncasecmp.c */ #include <string.h> #include <ctype.h> int strncasecmp(const char *s1, const char *s2, size_t n) { const unsigned char *c1 = (const unsigned char *)s1; const unsigned char *c2 = (const unsigned char *)s2; unsigned char ch; int d = 0; while (n--) { /* toupper() expects an unsigned char (implicitly cast to int) as input, and returns an int, which is exactly what we want. */ d = toupper(ch = *c1++) - toupper(*c2++); if (d || !ch) break; } return d; }