linkat — create a file link relative to directory file descriptors
#define _ATFILE_SOURCE #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h>
int
linkat( |
int | olddirfd, |
| const char * | oldpath, | |
| int | newdirfd, | |
| const char * | newpath, | |
| int | flags); |
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.
By default, linkat(), does
not dereference oldpath if it is a symbolic
link (like link(2)). Since Linux
2.6.18, 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.
On success, linkat() returns
0. On error, −1 is returned and errno is set to indicate the error.
The same errors that occur for link(2) can also occur for
linkat(). The following
additional errors can occur for linkat():
olddirfd or
newdirfd is not
a valid file descriptor.
oldpath is
relative and olddirfd is a file
descriptor referring to a file other than a directory;
or similar for newpath and newdirfd
This system call is non-standard but is proposed for inclusion in a future revision of POSIX.1.