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 *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);