-extern char *strchr(char *str, int character);
-extern char *strrchr(char *str, int character);
-extern char *strstr(char *str1, const char *str2);
+extern char *strndup(const char *src, int length);
+extern char *strchr(const char *str, int character);
+extern char *strrchr(const char *str, int character);
+extern char *strstr(const char *str1, const char *str2);
+extern size_t strcspn(const char *haystack, const char *reject);
+extern size_t strspn(const char *haystack, const char *accept);