extern char *strcpy(char *dst, const char *src);
extern char *strncpy(char *dst, const char *src, size_t num);
extern char *strcat(char *dst, const char *src);
+extern char *strncat(char *dest, const char *src, size_t n);
extern char *strdup(const char *src);
extern char *strndup(const char *src, size_t length);
extern char *strchr(const char *str, int character);