FILE
*
fopen(
const char * restrict path
, const char * restrict mode
)
FILE
*
fdopen(
int fildes
, const char *mode
)
FILE
*
freopen(
const char * restrict path
, const char * restrict mode
, FILE * restrict stream
)
)
function
opens the file whose name is the string pointed to by
path
and associates a stream with it.
The argument
mode
points to a string beginning with one of the following
sequences (Additional characters may follow these sequences.):
r
''
r+
''
w
''
w+
''
a
''
a+
''
The
mode
string can also include the letter ``b'' either as a last character or
as a character between the characters in any of the two-character strings
described above.
This is strictly for compatibility with
ANSI X3.159-1989 (``ANSI C89'')
and has no effect; the ``b'' is ignored.
The letter ``f'' in the mode string restricts fopen to regular
files; if the file opened is not a regular file,
fopen()
will fail.
This is a non
ANSI X3.159-1989 (``ANSI C89'')
extension.
Any created files will have mode
"S_IRUSR
|
S_IWUSR
|
S_IRGRP
|
S_IWGRP
|
S_IROTH
|
S_IWOTH
"
(0666
),
as modified by the process'
umask value (see
umask(2)).
Opening a file with append mode causes all subsequent writes to it to be forced to the then current end of file, regardless of intervening repositioning of the stream.
The
fopen()
and
freopen(
)
functions initially position the stream at the start of the file
unless the file is opened with append mode,
in which case the stream is initially positioned at the end of the file.
The
fdopen()
function associates a stream with the existing file descriptor,
fildes
.
The
mode
of the stream must be compatible with the mode of the file descriptor.
The stream is positioned at the file offset of the file descriptor.
The
freopen()
function
opens the file whose name is the string pointed to by
path
and associates the stream pointed to by
stream
with it.
The original stream (if it exists) is closed.
The
mode
argument is used just as in the
fopen()
function.
The primary use of the
freopen(
)
function
is to change the file associated with a
standard text stream
(stderr,
stdin,
or
stdout).
),
fdopen(
)
and
freopen(
)
return a
FILE
pointer.
Otherwise,
NULL
is returned and the global variable
errno
is set to indicate the error.
EINVAL
]
mode
provided to
fopen(
),
fdopen(
),
or
freopen(
)
was invalid.
EFTYPE
]
The
fopen(),
fdopen(
)
and
freopen(
)
functions
may also fail and set
errno
for any of the errors specified for the routine
malloc(3).
The
fopen()
function
may also fail and set
errno
for any of the errors specified for the routine
open(2).
The
fdopen()
function
may also fail and set
errno
for any of the errors specified for the routine
fcntl(2).
The
freopen()
function
may also fail and set
errno
for any of the errors specified for the routines
open(2),
fclose(3)
and
fflush(3).
)
and
freopen(
)
functions
conform to
ANSI X3.159-1989 (``ANSI C89'') .
The
fdopen(
)
function conforms to
ISO/IEC 9945-1:1990 (``POSIX.1'') .
)
with error checking should
close(2)
fildes
in case of failure, and
fclose(3)
the resulting FILE * in case of success.
FILE *file;
int fd;
if ((file = fdopen(fd, "r")) != NULL) {
/* perform operations on the FILE * */
fclose(file);
} else {
/* failure, report the error */
close(fd);
}