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 (con-
       sult 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 path-
       names  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  typi-
       cally  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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   FATTACH(3P)