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 fdopen()                Open a Stream Using a Handle

 #include   <stdio.h>

 FILE       *fdopen(handle,type);        Pointer to open stream
 int        handle;                      Handle referring to open file
 char       *type;                       Type of access permitted

    fdopen() associates a stream with a file 'handle' obtained from
    creat(), open(), dup(), or dup2(), thereby allowing a file opened for
    low-level I/O to be buffered and formatted.  'type' specifies the
    type of access requested for the file.  The specified 'type' must
    match the access mode with which the file was opened:

        "r"     Open for reading only.  The file must exist.

        "w"     Create a new file for writing, or open an existing file
                for writing.  Use with care: If the file already exists,
                its contents will be destroyed.

        "a"     Append.  Open for writing at the end-of-file, or create
                for writing if the file doesn't exist.  Existing data
                cannot be overwritten in this mode.

        "r+"    Update. Open an existing file for reading and writing;
                the file must exist.

        "w+"    Open an empty file for reading and writing. Use with
                care: If the file exists, its contents will be destroyed.

        "a+"    Open for reading and appending; create the file if it
                doesn't exist.  All write operations take place at the
                end of the file; existing data cannot be overwritten.

    The following characters may be appended to the above 'type' to
    specify the translation mode for the new lines:

        t       Open in text (translated) mode; The CR-LF pair is
                translated into a single LF on input; LF is translated to
                CR-LF on output.

        b       Open in binary (untranslated) mode.  The above
                translation is suppressed.

    If 't' or 'b' is not specified, the translation mode is defined by
    the default mode variable '_fmode'.  '_fmode' can be set to O_BINARY,
    binary mode, or O_TEXT, text mode.  These constants are defined in
    <fcntl.h>.

       Returns:     A pointer to the open stream.  NULL is returned on
                    error.

         Notes:     Both reading and writing are allowed when "r+", "w+"
                    or "a+" are used.  However, you must have an
                    intervening fseek or rewind operation when switching
                    between reading and writing (or vice versa).  Writing
                    can immediately follow reading only when the read
                    encountered EOF.

   -------------------------------- Example ---------------------------------

    This example opens a file in read only mode, then associates a stream
    with the open file handle:

           #include <stdio.h>
           #include <fcntl.h>

           FILE *stream;
           int fhndl;

           main()
           {
               fhndl = open("input.txt",O_RDONLY);
               .
               .
               .
               stream = fdopen(fhndl,"r");
           }