связать поток с файловым дескриптором (associate a stream with a file descriptor)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
fdopen — associate a stream with a file descriptor
Синопсис (Synopsis)
#include <stdio.h>
FILE *fdopen(int fildes, const char *mode);
Описание (Description)
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 last data access
timestamp 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.
Возвращаемое значение (Return value)
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.
Ошибки (Error)
The fdopen() function shall fail if:
EMFILE {STREAM_MAX} streams are currently open in the calling
process.
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.
ENOMEM Insufficient space to allocate a buffer.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
File descriptors are obtained from calls like open(), dup(),
creat(), or pipe(), which open files but do not return streams.
Обоснование (Rationale)
The file descriptor may have been obtained from open(), creat(),
pipe(), dup(), fcntl(), or socket(); inherited through fork(),
posix_spawn(), or exec; or perhaps obtained by other means.
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 POSIX.1‐2017, a good implementation of
append (a) mode would cause the O_APPEND flag to be set.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.5.1, Interaction of File Descriptors and Standard I/O
Streams, fclose(3p), fmemopen(3p), fopen(3p), open(3p),
open_memstream(3p), posix_spawn(3p), socket(3p)
The Base Definitions volume of POSIX.1‐2017, stdio.h(0p)
