# fattach

## 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.
    


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