fattach

       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

       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.
       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(P)