1 #include <string.h> 2 3 /* Return pointer to first occurrence of s2 in s1, NULL if none */ 4 5 char 6 *strstr(const char *s1, const char *s2) 7 { 8 char *p; 9 int f, n; 10 11 f = s2[0]; 12 if(f == 0) 13 return (char *)s1; 14 n = strlen(s2); 15 for(p=strchr(s1, f); p; p=strchr(p+1, f)) 16 if(strncmp(p, s2, n) == 0) 17 return p; 18 return NULL; 19 } 20 21