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 bitwise ORed in flags:

       AT_EMPTY_PATH (since Linux 2.6.39)
              If  oldpath  is  an  empty string, create a link to the file referenced 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 discussion 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 3.54 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/.