stringc.c

   1 #include <string.h>
   2
   3 char *strncpy(char *d, char *s, int n)
   4 {
   5         int len = strlen(s);
   6         if (len > n)
   7                 len = n;
   8         memcpy(d, s, len);
   9         memset(d + len, 0, n - len);
  10         return d;
  11 }
  12
  13 char *strcat(char *d, char *s)
  14 {
  15         strcpy(d + strlen(d), s);
  16         return d;
  17 }
  18
  19 char *strstr(char *s, char *r)
  20 {
  21         int len = strlen(r);
  22         if (!len)
  23                 return s;
  24         while (s) {
  25                 if (!memcmp(s, r, len))
  26                         return s;
  27                 s = strchr(s + 1, *r);
  28         }
  29         return NULL;
  30 }