extern int vsprintf(char *buf, const char *format, va_list args);
extern int sprintf(char *buf, const char *format, ...);
extern int snprintf(char *buf, size_t maxlen, const char *format, ...);
extern int vsprintf(char *buf, const char *format, va_list args);
extern int sprintf(char *buf, const char *format, ...);
extern int snprintf(char *buf, size_t maxlen, const char *format, ...);