Provided by: manpages-posix-dev_2017a-2_all bug

PROLOG

       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

       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 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);

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 .