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FATTACH(3P) POSIX Programmer's Manual FATTACH(3P)
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.
fattach — attach a STREAMS-based file descriptor to a file in the
file system name space (STREAMS)
#include <stropts.h>
int fattach(int fildes, const char *path);
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.
Upon successful completion, fattach() shall return 0. Otherwise, −1
shall be returned and errno set to indicate the 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.
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);
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.
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.
The fattach() function may be removed in a future version.
fdetach(3p), isastream(3p)
The Base Definitions volume of POSIX.1‐2008, stropts.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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 .
IEEE/The Open Group 2013 FATTACH(3P)
Pages that refer to this page: stropts.h(0p), close(3p), fdetach(3p)