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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.
NAME
fattach — attach a STREAMS-based file descriptor to a file in the file system name space
(STREAMS)
SYNOPSIS
#include <stropts.h>
int fattach(int fildes, const char *path);
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.
RETURN VALUE
Upon successful completion, fattach() shall return 0. Otherwise, -1 shall be returned and
errno set to indicate the error.
ERRORS
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.
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);
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.
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.
FUTURE DIRECTIONS
The fattach() function may be removed in a future version.
SEE ALSO
fdetach(), isastream()
The Base Definitions volume of POSIX.1‐2017, <stropts.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1-2017, Standard for Information Technology -- Portable Operating System Interface
(POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .
Any typographical or formatting errors that appear in this page are most likely to have
been introduced during the conversion of the source files to man page format. To report
such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .