— make hard link to a
char *name1, const char
fd1, const char
*name1, int fd2,
const char *name2,
function atomically creates the specified directory entry (hard link)
name2 with the attributes of the underlying object
pointed at by name1. If the link is successful: the
link count of the underlying object is incremented;
name1 and name2 share equal
access and rights to the underlying object.
If name1 is removed, the file name2 is not deleted and the link count of the underlying object is decremented.
name1 must exist for the hard link to succeed and both name1 and name2 must be in the same file system. As mandated by POSIX.1 name1 may not be a directory.
function is equivalent to
link() except that where
name1 or name2 specifies a
relative path, the directory entries linked are resolved relative to the
directories associated with file descriptors fd1 or
fd2 (respectively) instead of the current working
is passed the special value
AT_FDCWD (defined in
<fcntl.h>) in the
fd1 or fd2 parameter, the
current working directory is used for resolving the respective
name1 or name2 argument.
The flag argument is the bitwise OR of zero or more of the following values:
- If name1 names a symbolic link, a new link for the target of the symbolic link is created.
AT_SYMLINK_FOLLOW flag is clear and
name1 names a symbolic link, a new link is created for
the symbolic link name1 and not its target.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
linkat() will fail and no link will be created
- A component of either path prefix is not a directory.
- A component of a pathname exceeded
NAME_MAXcharacters, or an entire pathname (including the terminating NUL) exceeded
- A component of either path prefix does not exist.
- The file system containing the file named by name1 does not support links.
- The link count of the file named by name1 would
- A component of either path prefix denies search permission.
- The requested link requires writing in a directory with a mode that denies write permission.
- Too many symbolic links were encountered in translating one of the pathnames.
- The file named by name1 does not exist.
- The link named by name2 does exist.
- The file named by name1 is a directory and the
effective user ID is not superuser, or the file system containing the file
does not permit the use of
link() on a directory.
- The file named by name1 is flagged immutable or append-only.
- The link named by name2 and the file named by name1 are on different file systems.
- The directory in which the entry for the new link is being placed cannot be extended because there is no space left on the file system containing the directory.
- The directory in which the entry for the new link is being placed cannot be extended because the user's quota of disk blocks on the file system containing the directory has been exhausted.
- An I/O error occurred while reading from or writing to the file system to make the directory entry.
- The requested link requires writing in a directory on a read-only file system.
- One of the pathnames specified is outside the process's allocated address space.
linkat() will fail if:
- The value of the flag argument was neither zero nor
- The name1 or name2 argument
specifies a relative path and the fd1 or
fd2 argument, respectively, is neither
AT_FDCWDnor a valid file descriptor.
- The name1 or name2 argument specifies a relative path and the fd1 or fd2 argument, respectively, is a valid file descriptor but it does not reference a directory.
- The name1 or name2 argument specifies a relative path but search permission is denied for the directory which the fd1 or fd2 file descriptor, respectively, references.
ln(1), readlink(2), symlink(2), unlink(2)
linkat() functions are expected to conform to
IEEE Std 1003.1-2008 (“POSIX.1”).
link() system call first appeared in
Version 1 AT&T UNIX. The
linkat() function appeared in