huschi.net

LINKAT(2)                  Linux Programmer's Manual                 LINKAT(2)

NAME
       linkat - create a file link relative to directory file descriptors
SYNOPSIS
       #include <fcntl.h> /* Definition of AT_* constants */
       #include <unistd.h>
       int linkat(int olddirfd, const char *oldpath,
                  int newdirfd, const char *newpath, int flags);
   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
       linkat():
           Since glibc 2.10:
               _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _ATFILE_SOURCE
DESCRIPTION
       The  linkat()  system call operates in exactly the same way as link(2),
       except for the differences described in this manual page.
       If the pathname given in oldpath is relative, then  it  is  interpreted
       relative  to  the directory referred to by the file descriptor olddirfd
       (rather than relative to the current working directory of  the  calling
       process, as is done by link(2) for a relative pathname).
       If oldpath is relative and olddirfd is the special value AT_FDCWD, then
       oldpath is interpreted relative to the current working directory of the
       calling process (like link(2)).
       If oldpath is absolute, then olddirfd is ignored.
       The interpretation of newpath is as for oldpath, except that a relative
       pathname is interpreted relative to the directory referred  to  by  the
       file descriptor newdirfd.
       The following values can be biwise ORed in flags:
       AT_EMPTY_PATH (since Linux 2.6.39)
              If  oldpath is an empty string, create a link to the file refer-
              enced by olddirfd  (which  may  have  been  obtained  using  the
              open(2)  O_PATH  flag).  In this case, olddirfd can refer to any
              type of file, not just a directory.  The caller  must  have  the
              CAP_DAC_READ_SEARCH  capability  in order to use this flag; this
              prevents arbitrary users from creating  hard  links  using  file
              descriptors  received  via a UNIX domain socket (see the discus-
              sion of SCM_RIGHTS in unix(7)).
       AT_SYMLINK_FOLLOW (since Linux 2.6.18)
              By default, linkat(), does not dereference oldpath if  it  is  a
              symbolic link (like link(2)).  The flag AT_SYMLINK_FOLLOW can be
              specified in flags to cause oldpath to be dereferenced if it  is
              a symbolic link.
       Before  kernel  2.6.18,  the  flags  argument was unused, and had to be
       specified as 0.
RETURN VALUE
       On success, linkat() returns 0.  On error, -1 is returned and errno  is
       set to indicate the error.
ERRORS
       The  same  errors  that  occur for link(2) can also occur for linkat().
       The following additional errors can occur for linkat():
       EBADF  olddirfd or newdirfd is not a valid file descriptor.
       ENOENT AT_EMPTY_PATH was specified in flags, but  the  caller  did  not
              have the CAP_DAC_READ_SEARCH capability.
       ENOTDIR
       ENOTDIR
              oldpath  is relative and olddirfd is a file descriptor referring
              to a file other than a directory; or  similar  for  newpath  and
              newdirfd
VERSIONS
       linkat() was added to Linux in kernel 2.6.16; library support was added
       to glibc in version 2.4.
CONFORMING TO
       POSIX.1-2008.
NOTES
       See openat(2) for an explanation of the need for linkat().
SEE ALSO
       link(2), openat(2), path_resolution(7), symlink(7)
COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux                             2013-07-21                         LINKAT(2)