1 /* 2 * strcasecmp.c 3 */ 4 5 #include <string.h> 6 #include <ctype.h> 7 strcasecmp(const char * s1,const char * s2)8int strcasecmp(const char *s1, const char *s2) 9 { 10 const unsigned char *c1 = (const unsigned char *)s1; 11 const unsigned char *c2 = (const unsigned char *)s2; 12 unsigned char ch; 13 int d = 0; 14 15 while (1) { 16 /* toupper() expects an unsigned char (implicitly cast to int) 17 as input, and returns an int, which is exactly what we want. */ 18 d = toupper(ch = *c1++) - toupper(*c2++); 19 if (d || !ch) 20 break; 21 } 22 23 return d; 24 } 25