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); |
![[Note]](../stylesheet/note.png) |
Note | |||||
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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
oldpathis an empty string, create a link to the file referenced byolddirfd(which may have been obtained using the open(2)O_PATHflag). In this case,olddirfdcan refer to any type of file, not just a directory. The caller must have theCAP_DAC_READ_SEARCHcapability 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 ofSCM_RIGHTSin unix(7)). AT_SYMLINK_FOLLOW(since Linux 2.6.18)-
By default,
linkat(), does not dereferenceoldpathif it is a symbolic link (like link(2)). The flagAT_SYMLINK_FOLLOWcan be specified inflagsto causeoldpathto 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
-
olddirfdornewdirfdis not a valid file descriptor. - ENOENT
-
AT_EMPTY_PATHwas specified inflags, but the caller did not have theCAP_DAC_READ_SEARCHcapability. - ENOTDIR
- ENOTDIR
-
oldpathis relative andolddirfdis a file descriptor referring to a file other than a directory; or similar fornewpathandnewdirfd
VERSIONS
linkat() was added to Linux
in kernel 2.6.16; library support was added to glibc in
version 2.4.
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/.
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This manpage is Copyright (C) 2006, Michael Kerrisk %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |