The link() function creates a new link (directory entry) for the existing file and increments its link count by one. The existing argument points to a path name naming an existing file. The new argument points to a pathname naming the new directory entry to be created.

To create hard links, both files must be on the same file system. Both the old and the new link share equal access and rights to the underlying object. The super-user may make multiple links to a directory. Unless the caller is the super-user, the file named by existing must not be a directory.

Upon successful completion, link() marks for update the st_ctime field of the file. Also, the st_ctime and st_mtime fields of the directory that contains the new entry are marked for update.

Upon successful completion, 0 is returned. Otherwise, -1 is returned, no link is created, and errno is set to indicate the error.

The link() function will fail 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 where the entry for the new link is being placed cannot be extended because the user's quota of disk blocks on that file system has been exhausted.

EEXIST

The link named by new exists.

EFAULT

The existing or new argument points to an illegal address.

EINTR

A signal was caught during the execution of the link() function.

ELOOP

Too many symbolic links were encountered in translating path.

EMLINK

The maximum number of links to a file would be exceeded.

ENAMETOOLONG

The length of the existing or new argument exceeds PATH_MAX, or the length of a existing or new component exceeds NAME_MAX while _POSIX_NO_TRUNC is in effect.

ENOENT

The existing or new argument is a null pathname; a component of either path prefix does not exist; or the file named by existing does not exist.

ENOLINK

The existing or new argument points to a remote machine and the link to that machine is no longer active.

ENOSPC

The directory that would contain the link cannot be extended.

ENOTDIR

A component of either path prefix is not a directory.

EPERM

The file named by existing is a directory and the effective user of the calling process is not super-user.

EROFS

The requested link requires writing in a directory on a read-only file system.

EXDEV

The link named by new and the file named by existing are on different logical devices (file systems).

See attributes(5) for descriptions of the following attributes:

symlink(2), unlink(2), attributes(5)