fattach(3p) — Linux manual page


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

PROLOG         top

       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         top

       fattach — attach a STREAMS-based file descriptor to a file in the
       file system name space (STREAMS)

SYNOPSIS         top

       #include <stropts.h>

       int fattach(int fildes, const char *path);

DESCRIPTION         top

       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

       File descriptors referring to the underlying file, opened prior
       to an fattach() call, shall continue to refer to the underlying

RETURN VALUE         top

       Upon successful completion, fattach() shall return 0. Otherwise,
       -1 shall be returned and errno set to indicate the error.

ERRORS         top

       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.

              The length of a component of a pathname is longer than

       ENOENT A component of path does not name an existing file or path
              is an empty string.

              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>

       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.

              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         top

   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 *pathname = "/tmp/named-STREAM";
               int ret;

               ret = fattach(fd, pathname);


       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         top

       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.


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

SEE ALSO         top

       fdetach(3p), isastream(3p)

       The Base Definitions volume of POSIX.1‐2017, stropts.h(0p)

COPYRIGHT         top

       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(3P)

Pages that refer to this page: stropts.h(0p)close(3p)fdetach(3p)