FDOPEN(3C) Standard C Library Functions FDOPEN(3C)
NAME
fdopen - associate a stream with a file descriptor
SYNOPSIS
#include <stdio.h>
FILE *fdopen(
int fildes,
const char *mode);
DESCRIPTION
The
fdopen() function associates a stream with a file descriptor
fildes.
The
mode argument is a character string having one of the following
values:
r or
rb Open a file for reading.
w or
wb Open a file for writing.
a or
ab Open a file for writing at end of file.
r+,
rb+ or
r+b Open a file for update (reading and
writing).
w+,
wb+ or
w+b Open a file for update (reading and
writing).
a+,
ab+ or
a+b Open a file for update (reading and
writing) at end of file.
The meaning of these flags is exactly as specified for the
fopen(3C) function, except that modes beginning with
w do not cause truncation
of the file. A trailing
F character can also be included in the
mode argument as described in
fopen(3C) to enable extended FILE facility.
The mode of the stream must be allowed by the file access mode of the
open file. The file position indicator associated with the new stream
is set to the position indicated by the file offset associated with
the file descriptor.
The
fdopen() function preserves the offset maximum previously set for
the open file description corresponding to
fildes.
The error and end-of-file indicators for the stream are cleared. The
fdopen() function may cause the
st_atime field of the underlying file
to be marked for update.
If
fildes refers to a shared memory object, the result of the
fdopen() function is unspecified.
RETURN VALUES
Upon successful completion,
fdopen() returns a pointer to a stream.
Otherwise, a null pointer is returned and
errno is set to indicate
the error.
The
fdopen() function may fail and not set
errno if there are no free
stdio streams.
ERRORS
The
fdopen() function may fail if:
EBADF The
fildes argument is not a valid file descriptor.
EINVAL The
mode argument is not a valid mode.
EMFILE {
FOPEN_MAX} streams are currently open in the calling
process.
{
STREAM_MAX} streams are currently open in the calling
process.
ENOMEM There is insufficient space to allocate a buffer.
USAGE
A process is allowed to have at least {
FOPEN_MAX}
stdio streams open
at a time. For 32-bit applications, however, the underlying ABIs
formerly required that no file descriptor used to access the file
underlying a
stdio stream have a value greater than 255. To maintain
binary compatibility with earlier Solaris releases, this limit still
constrains 32-bit applications.
File descriptors are obtained from calls like
open(2),
dup(2),
creat(2) or
pipe(2), which open files but do not return streams.
Streams are necessary input for almost all of the standard I/O
library functions.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | See below. |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+
The
F character in the
mode argument is Evolving. In all other
respects this function is Standard.
SEE ALSO
creat(2),
dup(2),
open(2),
pipe(2),
fclose(3C),
fopen(3C),
attributes(7),
standards(7) April 18, 2006 FDOPEN(3C)
