.\" $NetBSD: link.2,v 1.33 2019/09/01 19:52:32 sevan Exp $ .\" .\" Copyright (c) 1980, 1991, 1993, 2011 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)link.2 8.3 (Berkeley) 1/12/94 .\" .Dd September 1, 2019 .Dt LINK 2 .Os .Sh NAME .Nm link .Nd make a hard file link .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In unistd.h .Ft int .Fn link "const char *name1" "const char *name2" .In fcntl.h .Ft int .Fn linkat "int fd1" "const char *name1" "int fd2" "const char *name2" "int flags" .Sh DESCRIPTION The .Fn link function call atomically creates the specified directory entry (hard link) .Fa name2 with the attributes of the underlying object pointed at by .Fa name1 . If the link is successful: the link count of the underlying object is incremented; .Fa name1 and .Fa name2 share equal access and rights to the underlying object. .Pp If .Fa name1 is removed, the file .Fa name2 is not deleted and the link count of the underlying object is decremented. .Pp .Fa name1 must exist for the hard link to succeed and both .Fa name1 and .Fa name2 must be in the same file system. .Fa name1 may not be a directory unless the caller is the super-user and the file system containing it supports linking to directories. .Pp .Fn linkat works the same way as .Fn link except if .Fa name1 (resp. .Fa name2 ) is relative. In that case, it is looked up from a directory whose file descriptor was passed as .Fa fd1 (resp. .Fa fd2 ) . Search permission is required on the directories named by .Fa fd1 and .Fa fd2 . .\" (These alternatives await a decision about the semantics of O_SEARCH) .\" Search permission is required on the directories named by .\" .Fa fd1 .\" and .\" .Fa fd2 .\" unless they were opened with the .\" .Dv O_SEARCH .\" flag. .\" - or - .\" The directories named by .\" .Fa fd1 .\" and .\" .Fa fd2 .\" must have been opened with the .\" .Dv O_SEARCH .\" flag. .Fa fd1 or .Fa fd2 can be set to .Dv AT_FDCWD in order to specify the current directory. .Pp When operating on a symlink, .Fn link resolves the symlink and creates a hard link on the target. .Fn linkat will do the same if .Dv AT_SYMLINK_FOLLOW is set in .Fa flags , but it will link on the symlink itself if the flag is clear. .Sh RETURN VALUES .Rv -std link linkat .Sh ERRORS .Fn link and .Fn linkat will fail and no link will be created if: .Bl -tag -width Er .It Bq Er 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. .It Bq Er 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. .It Bq Er EEXIST The link named by .Fa name2 does exist. .It Bq Er EFAULT One of the pathnames specified is outside the process's allocated address space. .It Bq Er EIO An I/O error occurred while reading from or writing to the file system to make the directory entry. .It Bq Er ELOOP Too many symbolic links were encountered in translating one of the pathnames. .It Bq Er EMLINK The link count of the file named by .Fa name1 would exceed .Brq Dv LINK_MAX . .It Bq Er ENAMETOOLONG A component of a pathname exceeded .Brq Dv NAME_MAX characters, or an entire path name exceeded .Brq Dv PATH_MAX characters. .It Bq Er ENOENT A component of either path prefix does not exist, or the file named by .Fa name1 does not exist. .It Bq Er 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. .It Bq Er ENOTDIR A component of either path prefix is not a directory. .It Bq Er EOPNOTSUPP The file system containing the file named by .Fa name1 does not support links. .It Bq Er EPERM The file named by .Fa 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 .Fn link on a directory. .It Bq Er EROFS The requested link requires writing in a directory on a read-only file system. .It Bq Er EXDEV The link named by .Fa name2 and the file named by .Fa name1 are on different file systems. .El .Pp In addition, .Fn linkat will fail if: .Bl -tag -width Er .It Bq Er EBADF .Fa name1 or .Fa name2 does not specify an absolute path and .Fa fd1 or .Fa fd2 , respectively, is neither .Dv AT_FDCWD nor a valid file descriptor open for reading or searching. .It Bq Er ENOTDIR .Fa name1 or .Fa name2 is not an absolute path and .Fa fd1 or .Fa fd2 , respectively, is a file descriptor associated with a non-directory file. .El .Sh SEE ALSO .Xr symlink 2 , .Xr unlink 2 .Sh STANDARDS The .Fn link function conforms to .St -p1003.1-90 . .Fn linkat conforms to .St -p1003.1-2008 . .Sh HISTORY The .Fn link function appeared in .At v1 .