trusty (2) linkat.2.gz

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/.