_fdopen, _wfdopen
Remonter à Stdio.h - Index
Header File
stdio.h
Category
Input/output Routines
Prototype
FILE *_fdopen(int handle, char *type);
FILE *_wfdopen(int handle, wchar_t *type);
Description
Associates a stream with a file handle.
_fdopen associates a stream with a file handle obtained from creat, dup, dup2, or open.
The type of stream must match the mode of the open handle.
The type string used in a call to _fdopen is one of the following values:
r | Open for reading only. _fdopen returns NULL if the file cannot be opened. | w | Create for writing. If the file already exists, its contents are overwritten. | a | Append; open for writing at end-of-file or create for writing if the file does not exist. | r+ | Open an existing file for update (reading and writing). _fdopen returns NULL if the file cannot be opened. | w+ | Create a new file for update. If the file already exists, its contents are overwritten. | a+ | Open for append; open (or create if the file does not exist) for update at the end of the file. |
---|
To specify that a given file is being opened or created in text mode, append t to the value of the type string (for example, rt or w+t).
Similarly, to specify binary mode, append b to the type string (for example, rb or w+b).
If t or b is not given in the type string, the mode is governed by the global variable _fmode.
If _fmode is set to O_BINARY, files will be opened in binary mode.
If _fmode is set to O_TEXT, files will be opened in text mode.
Note:The O_... constants are defined in fcntl.h.
When a file is opened for update, both input and output can be done on the resulting stream; however,
- output cannot be directly followed by input without an intervening fseek or rewind
- input cannot be directly followed by output without an intervening fseek, rewind, or an input that encounters end-of-file
Return Value
On successful completion _fdopen returns a pointer to the newly opened stream. In the event of error it returns NULL.
Example
#include <sys\stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
int handle;
FILE *stream;
/* open a file */
handle = open("DUMMY.FIL", O_CREAT,
S_IREAD | S_IWRITE);
/* now turn the handle into a stream */
stream = fdopen(handle, "w");
if (stream == NULL)
printf("fdopen failed\n");
else
{
fprintf(stream, "Hello world\n");
fclose(stream);
}
return 0;
}
Portability
POSIX | Win32 | ANSI C | ANSI C++ | |
---|---|---|---|---|
_fdopen |
+ |
+ |
||
_wfdopen |
+ |