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 void perror(const char *s);
extern FILE *fopen(const char *file, const char *mode);
extern FILE *freopen(const char *file, const char *mode, FILE *fp);
extern void fflush(FILE *fp);
extern off_t ftell(FILE *fp);
extern int fseek(FILE *fp, long int amt, int whence);
+extern void clearerr(FILE *stream);
+extern int feof(FILE *stream);
+extern int ferror(FILE *stream);
+extern int fileno(FILE *stream);
extern size_t fread(void *buf, size_t size, size_t n, FILE *fp);
extern size_t fwrite(void *buf, size_t size, size_t n, FILE *fp);