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 .