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FATTACH
Section: POSIX Programmer's Manual (3P)
Updated: 2003
Index
Return to Main Contents
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 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 .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- Attaching a File Descriptor to a File
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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