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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.
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 .

IEEE/The Open Group                  2003                          FATTACH(3P)