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



PPRROOLLOOGG
       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.

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

SSYYNNOOPPSSIISS
       #include <stropts.h>

       int fattach(int _f_i_l_d_e_s, const char *_p_a_t_h);

DDEESSCCRRIIPPTTIIOONN
       The _f_a_t_t_a_c_h() function shall attach a STREAMS-based file descriptor to
       a file, effectively associating a pathname with _f_i_l_d_e_s.  The
       application shall ensure that the _f_i_l_d_e_s argument is a valid open file
       descriptor associated with a STREAMS file. The _p_a_t_h argument points to
       a pathname of an existing file. The application shall have appropriate
       privileges or be the owner of the file named by _p_a_t_h and have write
       permission. A successful call to _f_a_t_t_a_c_h() shall cause all pathnames
       that name the file named by _p_a_t_h to name the STREAMS file associated
       with _f_i_l_d_e_s, 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 _p_a_t_h, the number of links is set to 1, and the
       size and device identifier are set to those of the STREAMS file
       associated with _f_i_l_d_e_s.  If any attributes of the named STREAMS file
       are subsequently changed (for example, by _c_h_m_o_d()), neither the
       attributes of the underlying file nor the attributes of the STREAMS
       file to which _f_i_l_d_e_s refers shall be affected.

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

RREETTUURRNN VVAALLUUEE
       Upon successful completion, _f_a_t_t_a_c_h() shall return 0. Otherwise, -1
       shall be returned and _e_r_r_n_o set to indicate the error.

EERRRROORRSS
       The _f_a_t_t_a_c_h() function shall fail if:

       EEAACCCCEESS Search permission is denied for a component of the path prefix,
              or the process is the owner of _p_a_t_h but does not have write
              permissions on the file named by _p_a_t_h.

       EEBBAADDFF  The _f_i_l_d_e_s argument is not a valid open file descriptor.

       EEBBUUSSYY  The file named by _p_a_t_h is currently a mount point or has a
              STREAMS file attached to it.

       EELLOOOOPP  A loop exists in symbolic links encountered during resolution of
              the _p_a_t_h argument.

       EENNAAMMEETTOOOOLLOONNGG
              The length of a component of a pathname is longer than
              {NAME_MAX}.

       EENNOOEENNTT A component of _p_a_t_h does not name an existing file or _p_a_t_h is an
              empty string.

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

       EEPPEERRMM  The effective user ID of the process is not the owner of the
              file named by _p_a_t_h and the process does not have appropriate
              privileges.

       The _f_a_t_t_a_c_h() function may fail if:

       EEIINNVVAALL The _f_i_l_d_e_s argument does not refer to a STREAMS file.

       EELLOOOOPP  More than {SYMLOOP_MAX} symbolic links were encountered during
              resolution of the _p_a_t_h argument.

       EENNAAMMEETTOOOOLLOONNGG
              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}.

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

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
   AAttttaacchhiinngg aa FFiillee DDeessccrriippttoorr ttoo aa FFiillee
       In the following example, _f_d refers to an open STREAMS file. The call
       to _f_a_t_t_a_c_h() associates this STREAM with the file //ttmmpp//nnaammeedd--SSTTRREEAAMM,
       such that any future calls to open //ttmmpp//nnaammeedd--SSTTRREEAAMM, prior to breaking
       the attachment via a call to _f_d_e_t_a_c_h(), will instead create a new file
       handle referring to the STREAMS file associated with _f_d.


           #include <stropts.h>
           ...
               int fd;
               char *pathname = "/tmp/named-STREAM";
               int ret;

               ret = fattach(fd, pathname);

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       The _f_a_t_t_a_c_h() function behaves similarly to the traditional _m_o_u_n_t()
       function in the way a file is temporarily replaced by the root
       directory of the mounted file system. In the case of _f_a_t_t_a_c_h(), the
       replaced file need not be a directory and the replacing file is a
       STREAMS file.

RRAATTIIOONNAALLEE
       The file attributes of a file which has been the subject of an
       _f_a_t_t_a_c_h() call are specifically set because of an artifact of the
       original implementation. The internal mechanism was the same as for the
       _m_o_u_n_t() function. Since _m_o_u_n_t() 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 _f_a_t_t_a_c_h()
       remains in effect.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       The _f_a_t_t_a_c_h() function may be removed in a future version.

SSEEEE AALLSSOO
       _f_d_e_t_a_c_h(), _i_s_a_s_t_r_e_a_m()

       The Base Definitions volume of POSIX.1-2017, <<ssttrrooppttss..hh>>

CCOOPPYYRRIIGGHHTT
       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)
