#include <fcntl.h> /* Definition of AT_* constants */
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)):
Since glibc 2.10:
_XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
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 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
ENOENT AT_EMPTY_PATH was specified in flags, but the caller did not
have the CAP_DAC_READ_SEARCH capability.
oldpath is relative and olddirfd is a file descriptor referring
to a file other than a directory; or similar for newpath and
linkat() was added to Linux in kernel 2.6.16; library support was added
to glibc in version 2.4.
See openat(2) for an explanation of the need for linkat().
link(2), openat(2), path_resolution(7), symlink(7)
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/.
Linux 2013-07-21 LINKAT(2)
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