Associates a file pointer with a file descriptor returned by an
open, creat, dup, dup2, or pipe function.
Format
#include <stdio.h>
FILE *fdopen (int file_desc, char *a_mode);
Arguments
- file_desc
- The file descriptor returned by open, creat, dup, dup2, or pipe.
- a_mode
- The access mode indicator. Use one of the following character
strings: "r", "w", "a", "r+", "w+", "rb", "r+b", "rb+", "wb", "w+b",
"wb+", "ab", "a+b", "ab+", or "a+".
These access modes have the following effects:
- "r" opens an existing file for reading.
- "w" creates a new file, if necessary, and opens the file
for writing. If the file exists, it creates a new file with the
same name and a higher version number.
- "a" opens the file for append access. An existing file
is positioned at the end-of-file, and data is written there. If
the file does not exist, the DEC C RTL
creates it.
The update access modes allow a file to be opened for both reading
and writing. When used with existing files, "r+" and "a+" differ
only in the initial positioning within the file. The modes are as
follows:
- "r+" opens an existing file for read update access. It is
opened for reading, positioned first at the beginning-of-file,
but writing is also allowed.
- "w+" opens a new file for write update access.
- "a+" opens a file for append update access. The file is
first positioned at the end-of-file (writing). If the file does
not exist, the DEC C RTL creates it.
- "b" means binary access mode. In this case, no conversion
of carriage-control information is attempted.
Description
This function allows you to access a file, originally opened
by one of the UNIX I/O functions, with Standard I/O functions.
Ordinarily, a file can be accessed by either a file descriptor or
by a file pointer, but not both, depending on the way you open it.
For more information, see Chapters 1 and
2.
Return Values
| pointer | Indicates that the
operation has succeeded. |
| NULL |
Indicates that an error has occurred. |
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