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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 dif-
       fer (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 path-
       name with fildes. The application shall ensure that the fildes argument is a valid open file descriptor associ-
       ated  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 success-
       ful call to fattach() shall cause all pathnames that name the file named by path to name the STREAMS file asso-
       ciated 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 attach-
       ment 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, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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)