основанный на файловом дескрипторе файл в пространстве имен файловой системы (STREAMS) (based file descriptor to a file in the file system name space (STREAMS))
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)
fattach — attach a STREAMS-based file descriptor to a file in the
file system name space (STREAMS)
Синопсис (Synopsis)
#include <stropts.h>
int fattach(int fildes, const char *path);
Описание (Description)
The fattach() function shall attach a STREAMS-based file
descriptor to a file, effectively associating a pathname with
fildes. The application shall ensure that the fildes argument is
a valid open file descriptor associated with a STREAMS file. The
path argument points to a pathname of an existing file. The
application shall have appropriate privileges or be the owner of
the file named by path and have write permission. A successful
call to fattach() shall cause all pathnames that name the file
named by path to name the STREAMS file associated with fildes,
until the STREAMS file is detached from the file. A STREAMS file
can be attached to more than one file and can have several
pathnames associated with it.
The attributes of the named STREAMS file shall be initialized as
follows: the permissions, user ID, group ID, and times are set to
those of the file named by path, the number of links is set to 1,
and the size and device identifier are set to those of the
STREAMS file associated with fildes. If any attributes of the
named STREAMS file are subsequently changed (for example, by
chmod()), neither the attributes of the underlying file nor the
attributes of the STREAMS file to which fildes refers shall be
affected.
File descriptors referring to the underlying file, opened prior
to an fattach() call, shall continue to refer to the underlying
file.
Возвращаемое значение (Return value)
Upon successful completion, fattach() shall return 0. Otherwise,
-1 shall be returned and errno set to indicate the error.
Ошибки (Error)
The fattach() function shall fail if:
EACCES Search permission is denied for a component of the path
prefix, or the process is the owner of path but does not
have write permissions on the file named by path.
EBADF The fildes argument is not a valid open file descriptor.
EBUSY The file named by path is currently a mount point or has a
STREAMS file attached to it.
ELOOP A loop exists in symbolic links encountered during
resolution of the path argument.
ENAMETOOLONG
The length of a component of a pathname is longer than
{NAME_MAX}.
ENOENT A component of path does not name an existing file or path
is an empty string.
ENOTDIR
A component of the path prefix names an existing file that
is neither a directory nor a symbolic link to a directory,
or the path argument contains at least one non-<slash>
character and ends with one or more trailing <slash>
characters.
EPERM The effective user ID of the process is not the owner of
the file named by path and the process does not have
appropriate privileges.
The fattach() function may fail if:
EINVAL The fildes argument does not refer to a STREAMS file.
ELOOP More than {SYMLOOP_MAX} symbolic links were encountered
during resolution of the path argument.
ENAMETOOLONG
The length of a pathname exceeds {PATH_MAX}, or pathname
resolution of a symbolic link produced an intermediate
result with a length that exceeds {PATH_MAX}.
EXDEV A link to a file on another file system was attempted.
The following sections are informative.
Примеры (Examples)
Attaching a File Descriptor to a File
In the following example, fd refers to an open STREAMS file. The
call to fattach() associates this STREAM with the file
/tmp/named-STREAM, such that any future calls to open /tmp/named-
STREAM, prior to breaking the attachment via a call to fdetach(),
will instead create a new file handle referring to the STREAMS
file associated with fd.
#include <stropts.h>
...
int fd;
char *pathname = "/tmp/named-STREAM";
int ret;
ret = fattach(fd, pathname);
Использование в приложениях (Application usage)
The fattach() function behaves similarly to the traditional
mount() function in the way a file is temporarily replaced by the
root directory of the mounted file system. In the case of
fattach(), the replaced file need not be a directory and the
replacing file is a STREAMS file.
Обоснование (Rationale)
The file attributes of a file which has been the subject of an
fattach() call are specifically set because of an artifact of the
original implementation. The internal mechanism was the same as
for the mount() function. Since mount() is typically only applied
to directories, the effects when applied to a regular file are a
little surprising, especially as regards the link count which
rigidly remains one, even if there were several links originally
and despite the fact that all original links refer to the STREAM
as long as the fattach() remains in effect.
Будущие направления (Future directions)
The fattach() function may be removed in a future version.
Смотри также (See also)
fdetach(3p), isastream(3p)
The Base Definitions volume of POSIX.1‐2017, stropts.h(0p)
