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 the 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 size of path exceeds {PATH_MAX} or a component of path 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 is not a directory.
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
privilege.
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
Pathname resolution of a symbolic link produced an intermediate
result whose length 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 *filename = "/tmp/named-STREAM";
int ret;
ret = fattach(fd, filename);
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 artefact 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
None.
SEE ALSO
fdetach() , isastream() , the Base Definitions volume of
IEEE Std 1003.1-2001, <stropts.h>
COPYRIGHT
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 .