NAME
link
—
make a hard file link
LIBRARY
library “libc”
SYNOPSIS
#include
<unistd.h>
int
link
(const
char *name1, const char
*name2);
#include
<fcntl.h>
int
linkat
(int
fd1, const char
*name1, int fd2,
const char *name2,
int flags);
DESCRIPTION
Thelink
()
function call 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. name1 may not be a directory unless the caller is the super-user and the file system containing it supports linking to directories.
linkat
()
works the same way as link
() except if
name1 (resp. name2) is relative.
In that case, it is looked up from a directory whose file descriptor was
passed as fd1 (resp. fd2).
Search permission is required on the directories named by
fd1 and fd2.
fd1 or fd2 can be set to
AT_FDCWD
in order to specify the current
directory.
When operating on a symlink,
link
()
resolves the symlink and creates a hard link on the target.
linkat
() will do the same if
AT_SYMLINK_FOLLOW
is set in
flags, but it will link on the symlink itself if the
flag is clear.
RETURN VALUES
The link
() and
linkat
() functions return the value 0 if
successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
ERRORS
link
() and
linkat
() will fail and no link will be created
if:
- [
EACCES
] - A component of either path prefix denies search permission, or the requested link requires writing in a directory with a mode that denies write permission.
- [
EDQUOT
] - 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.
- [
EEXIST
] - The link named by name2 does exist.
- [
EFAULT
] - One of the pathnames specified is outside the process's allocated address space.
- [
EIO
] - An I/O error occurred while reading from or writing to the file system to make the directory entry.
- [
ELOOP
] - Too many symbolic links were encountered in translating one of the pathnames.
- [
EMLINK
] - The link count of the file named by name1 would
exceed {
LINK_MAX
}. - [
ENAMETOOLONG
] - A component of a pathname exceeded {
NAME_MAX
} characters, or an entire path name exceeded {PATH_MAX
} characters. - [
ENOENT
] - A component of either path prefix does not exist, or the file named by name1 does not exist.
- [
ENOSPC
] - 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.
- [
ENOTDIR
] - A component of either path prefix is not a directory.
- [
EOPNOTSUPP
] - The file system containing the file named by name1 does not support links.
- [
EPERM
] - The file named by name1 is a directory and the
effective user ID is not super-user, or the file system containing the
file does not permit the use of
link
() on a directory. - [
EROFS
] - The requested link requires writing in a directory on a read-only file system.
- [
EXDEV
] - The link named by name2 and the file named by name1 are on different file systems.
In addition, linkat
() will fail if:
- [
EBADF
] - name1 or name2 does not
specify an absolute path and fd1 or
fd2, respectively, is neither
AT_FDCWD
nor a valid file descriptor open for reading or searching. - [
ENOTDIR
] - name1 or name2 is not an absolute path and fd1 or fd2, respectively, is a file descriptor associated with a non-directory file.
SEE ALSO
STANDARDS
The link
() function conforms to
IEEE Std 1003.1-1990 (“POSIX.1”).
linkat
() conforms to IEEE Std
1003.1-2008 (“POSIX.1”).
HISTORY
The link
() function appeared in
Version 1 AT&T UNIX.