Originální popis anglicky:
fdopen - associate a stream with a file descriptor
Návod, kniha: POSIX Programmer's Manual
#include <stdio.h>
FILE *fdopen(int
fildes, const char
*mode );
The
fdopen() function shall associate a stream with a file descriptor.
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+ or rb+ or r+b
- Open a file for update (reading and writing).
- w+ or wb+ or w+b
- Open a file for update (reading and writing).
- a+ or 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 in
fopen(), except
that modes beginning with
w shall not cause truncation of the file.
Additional values for the
mode argument may be supported by an
implementation.
The application shall ensure that the mode of the stream as expressed by the
mode argument is allowed by the file access mode of the open file
description to which
fildes refers. 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 error and end-of-file indicators for the stream shall be 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.
If
fildes refers to a typed memory object, the result of the
fdopen() function is unspecified.
The
fdopen() function shall preserve the offset maximum previously set
for the open file description corresponding to
fildes.
Upon successful completion,
fdopen() shall return a pointer to a stream;
otherwise, a null pointer shall be returned and
errno set to indicate
the error.
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.
- EMFILE
- {STREAM_MAX} streams are currently open in the calling
process.
- ENOMEM
- Insufficient space to allocate a buffer.
The following sections are informative.
None.
File descriptors are obtained from calls like
open(),
dup(),
creat(), or
pipe(), which open files but do not return streams.
The file descriptor may have been obtained from
open(),
creat(),
pipe(),
dup(), or
fcntl(); inherited through
fork() or
exec; or perhaps obtained by implementation-defined
means, such as the 4.3 BSD
socket() call.
The meanings of the
mode arguments of
fdopen() and
fopen()
differ. With
fdopen(), open for write (
w or
w+) does not
truncate, and append (
a or
a+) cannot create for writing. The
mode argument formats that include
a b are allowed for
consistency with the ISO C standard function
fopen(). The
b has no effect on the resulting stream. Although not explicitly
required by this volume of IEEE Std 1003.1-2001, a good
implementation of append (
a) mode would cause the O_APPEND flag to be
set.
None.
Interaction of File Descriptors and Standard I/O Streams ,
fclose() ,
fopen() ,
open() , the Base Definitions volume
of IEEE Std 1003.1-2001,
<stdio.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
