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(7).)
EDQUOT: The user's quota of disk blocks on the filesystem has been exhausted.
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.
EPERM (since Linux 3.6): The caller does not have permission to create a hard link to this file (see the description of /proc/sys/fs/protected_hardlink in proc(5)).
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() does not work across different mount points, even if the same filesystem is mounted on both.)

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001 (but see NOTES).

NOTES

Hard links, as created by link(), cannot span filesystems. Use symlink(2) if this is required.

POSIX.1-2001 says that link() should dereference oldpath if it is a symbolic link. However, since kernel 2.0, 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. POSIX.1-2008 changes the specification of link(), making it implementation-dependent whether or not oldpath is dereferenced if it is a symbolic link. For precise control over the treatment of symbolic links when creating a link, see linkat(2).

BUGS

On NFS filesystems, 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.

COLOPHON

This page is part of release 3.54 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

link (2)

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