FATTACH(3P) POSIX Programmer s Manual FATTACH(3P)

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 privi- leges or be the owner of the file named by path and have write permis- sion. 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 path- names associated with it.

The attributes of the named STREAMS file shall be initialized as fol- lows: 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 subse- quently 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 per- missions 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 direc- tory 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 fat- tach() 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, espe- cially as regards the link count which rigidly remains one, even if there were several links originally and despite the fact that all orig- inal links refer to the STREAM as long as the fattach() remains in effect.


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 .

IEEE/The Open Group 2003 FATTACH(3P)