int remove(const char *filename);
    int rename(const char *old, const char *new);
    FILE *tmpfile(void);
    char *tmpnam(char *s);
    int fclose(FILE *stream);
    int fflush(FILE *stream);
    FILE *fopen(const char *filename, const char *mode);
       file modes
    FILE *freopen(const char *filename, const char *mode, FILE *stream);
    int setvbuf(FILE *stream, char *buf, int mode, size_t size);
    void setbuf(FILE *stream, char *buf);
    int printf(const char *format, ...);
      printf format
    int fprintf(FILE *stream, const char *format, ...);
    int sprintf(char *s, const char * format, ...);
    int vfprintf(FILE *stream, const char *format, va_list arg);
    int vprintf(const char *format, va_list arg);
    int vsprintf(char *s, const char *format, va_list arg);
    int scanf(const char *format, ...);
      scanf format
    int fscanf(FILE *stream, const char *format, ...);
    int sscanf(const char *s, const char *format, ...);
    int fgetc(FILE *stream);
    int fgets(char *s, int n, FILE *stream);
    int fputc(int c, FILE *stream);
    int fputs(const char *s, FILE *stream);
    int getc(FILE *stream);
    int getchar(void);
    char *gets(char *s);
    int putc(int c, FILE *stream);
    int putchar(int c);
    int puts(const char *s);
    int ungetc(int c, FILE *stream);
    size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);
    size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream);
    int fgetpos(FILE *stream, fpos_t *pos);
    int fseek(FILE *stream, long int offset, int whence);
    int fsetpos(FILE *stream, const fpos_t *ps);
    long int ftell(FILE *stream);
    void rewind(FILE *stream);
    void clearerr(FILE *stream);
    int feof(FILE *stream);
    int ferrror(FILE *stream);
    void perror(const char *s);