NAME
linkat - create a file link relative to directory file descriptors SYNOPSIS
#include
/* Definition of AT* constants */ #include
int linkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags); Feature Test Macro Requirements for glibc (see featuretestmacros(7)): linkat(): Since glibc 2.10: XOPENSOURCE >= 700 || POSIXCSOURCE >= 200809L Before glibc 2.10: ATFILESOURCE 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 ATFDCWD, 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: ATEMPTYPATH (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) OPATH flag). In this case, olddirfd can refer to any type of file, not just a directory. The caller must have the CAPDACREADSEARCH 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 SCMRIGHTS in unix(7)). ATSYMLINKFOLLOW (since Linux 2.6.18) By default, linkat(), does not dereference oldpath if it is a symbolic link (like link(2)). The flag ATSYMLINKFOLLOW 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 ATEMPTYPATH was specified in flags, but the caller did not have the CAPDACREADSEARCH 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), pathresolution(7), symlink(7) COLOPHON
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Linux 2013-07-21 LINKAT(2)