Sets the file to its beginning.
    Format
      #include  <stdio.h>
      void rewind  (FILE *file_ptr); (ISO POSIX-1)
      int rewind  (FILE *file_ptr); (DEC C Extension)
1 – Argument
 file_ptr
    A file pointer.
2 – Description
    The rewind function is equivalent to fseek (file_ptr, 0, SEEK_
    SET). You can use the rewind function with either record or
    stream files.
    A successful call to rewind clears the error indicator for the
    file.
    The ANSI C standard defines rewind as not returning a value;
    therefore, the function prototype for rewind is declared with a
    return type of void. However, since a rewind can fail, and since
    previous versions of the Compaq C RTL have declared rewind to
    return an int, the code for rewind does return 0 on success and
    -1 on failure.
    See also fseek.