fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
289 lines
6.8 KiB
Groff
289 lines
6.8 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)link.2 8.3 (Berkeley) 1/12/94
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.\" $FreeBSD$
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.\"
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.Dd April 10, 2008
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.Dt LINK 2
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.Os
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.Sh NAME
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.Nm link ,
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.Nm linkat
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.Nd make a hard file link
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn link "const char *name1" "const char *name2"
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.Ft int
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.Fo linkat
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.Fa "int fd1" "const char *name1" "int fd2" "const char *name2" "int flag"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn link
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system call
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atomically creates the specified directory entry (hard link)
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.Fa name2
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with the attributes of the underlying object pointed at by
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.Fa name1 .
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If the link is successful: the link count of the underlying object
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is incremented;
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.Fa name1
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and
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.Fa name2
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share equal access and rights
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to the
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underlying object.
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.Pp
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If
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.Fa name1
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is removed, the file
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.Fa name2
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is not deleted and the link count of the
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underlying object is
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decremented.
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.Pp
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The object pointed at by the
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.Fa name1
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argument
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must exist for the hard link to
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succeed and
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both
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.Fa name1
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and
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.Fa name2
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must be in the same file system.
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The
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.Fa name1
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argument
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may not be a directory.
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.Pp
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The
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.Fn linkat
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system call is equivalent to
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.Fa link
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except in the case where either
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.Fa name1
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or
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.Fa name2
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or both are relative paths.
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In this case a relative path
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.Fa name1
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is interpreted relative to
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the directory associated with the file descriptor
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.Fa fd1
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instead of the current working directory and similarly for
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.Fa name2
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and the file descriptor
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.Fa fd2 .
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.Pp
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Values for
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.Fa flag
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are constructed by a bitwise-inclusive OR of flags from the following
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list, defined in
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.In fcntl.h :
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.Bl -tag -width indent
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.It Dv AT_SYMLINK_FOLLOW
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If
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.Fa name1
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names a symbolic link, a new link for the target of the symbolic link is
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created.
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.El
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.Pp
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If
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.Fn linkat
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is passed the special value
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.Dv AT_FDCWD
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in the
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.Fa fd1
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or
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.Fa fd2
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parameter, the current working directory is used for the respective
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.Fa name
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argument.
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If both
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.Fa fd1
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and
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.Fa fd2
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have value
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.Dv AT_FDCWD ,
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the behavior is identical to a call to
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.Fn link .
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Unless
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.Fa flag
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contains the
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.Dv AT_SYMLINK_FOLLOW
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flag, if
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.Fa name1
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names a symbolic link, a new link is created for the symbolic link
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.Fa name1
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and not its target.
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.Sh RETURN VALUES
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.Rv -std link
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.Sh ERRORS
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The
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.Fn link
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system call
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will fail and no link will be created if:
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.Bl -tag -width Er
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.It Bq Er ENOTDIR
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A component of either path prefix is not a directory.
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.It Bq Er ENAMETOOLONG
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A component of either pathname exceeded 255 characters,
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or entire length of either path name exceeded 1023 characters.
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.It Bq Er ENOENT
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A component of either path prefix does not exist.
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.It Bq Er EOPNOTSUPP
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The file system containing the file named by
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.Fa name1
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does not support links.
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.It Bq Er EMLINK
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The link count of the file named by
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.Fa name1
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would exceed 32767.
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.It Bq Er EACCES
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A component of either path prefix denies search permission.
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.It Bq Er EACCES
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The requested link requires writing in a directory with a mode
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that denies write permission.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating one of the pathnames.
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.It Bq Er ENOENT
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The file named by
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.Fa name1
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does not exist.
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.It Bq Er EEXIST
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The link named by
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.Fa name2
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does exist.
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.It Bq Er EPERM
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The file named by
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.Fa name1
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is a directory.
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.It Bq Er EPERM
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The file named by
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.Fa name1
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has its immutable or append-only flag set, see the
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.Xr chflags 2
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manual page for more information.
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.It Bq Er EPERM
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The parent directory of the file named by
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.Fa name2
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has its immutable flag set.
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.It Bq Er EXDEV
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The link named by
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.Fa name2
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and the file named by
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.Fa name1
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are on different file systems.
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.It Bq Er ENOSPC
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The directory in which the entry for the new link is being placed
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cannot be extended because there is no space left on the file
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system containing the directory.
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.It Bq Er EDQUOT
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The directory in which the entry for the new link
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is being placed cannot be extended because the
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user's quota of disk blocks on the file system
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containing the directory has been exhausted.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to
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the file system to make the directory entry.
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.It Bq Er EROFS
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The requested link requires writing in a directory on a read-only file
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system.
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.It Bq Er EFAULT
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One of the pathnames specified
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is outside the process's allocated address space.
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.El
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.Pp
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In addition to the errors returned by the
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.Fn link ,
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the
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.Fn linkat
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system call may fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa name1
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or
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.Fa name2
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argument does not specify an absolute path and the
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.Fa fd1
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or
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.Fa fd2
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argument, respectively, is neither
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.Dv AT_FDCWD
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nor a valid file descriptor open for searching.
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.It Bq Er EINVAL
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The value of the
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.Fa flag
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argument is not valid.
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.It Bq Er ENOTDIR
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The
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.Fa name1
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or
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.Fa name2
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argument is not an absolute path and
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.Fa fd1
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or
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.Fa fd2 ,
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respectively, is neither
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.Dv AT_FDCWD
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nor a file descriptor associated with a directory.
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.El
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.Sh SEE ALSO
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.Xr chflags 2 ,
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.Xr readlink 2 ,
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.Xr symlink 2 ,
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.Xr unlink 2
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.Sh STANDARDS
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The
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.Fn link
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system call is expected to conform to
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.St -p1003.1-90 .
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The
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.Fn linkat
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system call follows The Open Group Extended API Set 2 specification.
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.Sh HISTORY
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The
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.Fn link
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function appeared in
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.At v7 .
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The
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.Fn linkat
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system call appeared in
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.Fx 8.0 .
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.Pp
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The
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.Fn link
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system call traditionally allows the super-user to link directories which
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corrupts the file system coherency.
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This implementation no longer permits it.
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