LINK(2)

NAME
link - make a new name for a file

SYNOPSIS
#include <unistd.h>

int link(const char *oldpath, const char *newpath);

DESCRIPTION
link() creates a new link (also known as a hard link) to an existing file. If newpath exists it will not be overwritten. This new name may be used exactly as the old one for any operation; both names refer to the same file (and so have the same permissions and ownership) and it is impossible to tell which name was the `original'.

RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

ERRORS

EACCES
    Write access to the directory containing newpath is denied, or search permission is denied for one of the directories in the path prefix of oldpath or newpath. (See also path_resolution(2).)

EEXIST
    newpath already exists.

EFAULT
    oldpath or newpath points outside your accessible address space.

EIO An I/O error occurred.

ELOOP
    Too many symbolic links were encountered in resolving oldpath or newpath.

EMLINK
    The file referred to by oldpath already has the maximum number of links to it.

ENAMETOOLONG
    oldpath or newpath was too long.

ENOENT
    A directory component in oldpath or newpath does not exist or is a dangling symbolic link.

ENOMEM
    Insufficient kernel memory was available.

ENOSPC
    The device containing the file has no room for the new directory entry.

ENOTDIR
    A component used as a directory in oldpath or newpath is not, in fact, a directory.

EPERM
    oldpath is a directory.

EPERM
    The filesystem containing oldpath and newpath does not support the creation of hard links.

EROFS
    The file is on a read-only filesystem.

EXDEV
    oldpath and newpath are not on the same mounted filesystem. (Linux permits a filesystem to be mounted at multiple points, but link(2) does not work across different mount points, even if the same filesystem is mounted on both.)

NOTES
Hard links, as created by link(), cannot span filesystems. Use symlink() if this is required. POSIX.1-2001 says that link() should dereference oldpath if it is a symbolic link. However, Linux does not do so: if oldpath is a symbolic link, then newpath is created as a (hard) link to the same symbolic link file (i.e., newpath becomes a symbolic link to the same file that oldpath refers to). Some other implementations behave in the same manner as Linux.

CONFORMING TO
SVr4, SVID, POSIX, 4.3BSD, X/OPEN. SVr4 documents additional ENOLINK and EMULTIHOP error conditions; POSIX.1 does not document ELOOP. X/OPEN does not document EFAULT, ENOMEM or EIO.

BUGS
On NFS file systems, the return code may be wrong in case the NFS server performs the link creation and dies before it can say so. Use stat(2) to find out if the link got created.

SEE ALSO
ln(1), open(2), path_resolution(2), rename(2), stat(2), symlink(2), unlink(2)