FATTACH(3)                 POSIX Programmer's Manual                FATTACH(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 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 length of a component of a pathname 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 names an existing file that is
              neither a directory nor a symbolic link to a directory, or the
              path argument contains at least one non-<slash> character and
              ends with one or more trailing <slash> characters.

       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
              privileges.

       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
              The length of a pathname exceeds {PATH_MAX}, or pathname
              resolution of a symbolic link produced an intermediate result
              with a length that exceeds {PATH_MAX}.

       EXDEV  A link to a file on another file system was attempted.

       The following sections are informative.

EXAMPLES
   Attaching aa File Descriptor to aa 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 *pathname = "/tmp/named-STREAM";
               int ret;

               ret = fattach(fd, pathname);

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 artifact 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
       The fattach() function may be removed in a future version.

SEE ALSO
       fdetach(), isastream()

       The Base Definitions volume of POSIX.1-2017, <stropts.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                           FATTACH(3)
