Creates a temporary file that is opened for update.

    Format

      #include  <stdio.h>

      FILE *tmpfile  (void);

1 - Description

    The file exists only for the duration of the process, or until
    the file is closed and is preserved across calls to vfork.

2 - Return Values

    x                  The address of a file pointer (defined in the
                       <stdio.h> header file).
    NULL               Indicates an error.