1994-05-27 05:00:24 +00:00
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.\" 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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2017-02-28 23:42:47 +00:00
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.\" 3. Neither the name of the University nor the names of its contributors
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1994-05-27 05:00:24 +00:00
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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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1999-08-28 00:22:10 +00:00
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.\" $FreeBSD$
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1994-05-27 05:00:24 +00:00
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.\"
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2021-03-07 14:29:09 +00:00
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.Dd March 30, 2021
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1994-05-27 05:00:24 +00:00
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.Dt LINK 2
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2001-07-10 13:41:46 +00:00
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.Os
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1994-05-27 05:00:24 +00:00
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.Sh NAME
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2008-04-16 13:03:12 +00:00
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.Nm link ,
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.Nm linkat
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1994-05-27 05:00:24 +00:00
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.Nd make a hard file link
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2000-04-21 09:42:15 +00:00
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.Sh LIBRARY
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.Lb libc
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1994-05-27 05:00:24 +00:00
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.Sh SYNOPSIS
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2001-10-01 16:09:29 +00:00
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.In unistd.h
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1994-05-27 05:00:24 +00:00
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.Ft int
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.Fn link "const char *name1" "const char *name2"
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2008-04-16 13:03:12 +00:00
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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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1994-05-27 05:00:24 +00:00
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.Sh DESCRIPTION
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The
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.Fn link
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2002-12-18 09:22:32 +00:00
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system call
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1994-05-27 05:00:24 +00:00
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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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1998-01-15 04:31:28 +00:00
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.Fa name1 .
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1994-05-27 05:00:24 +00:00
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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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2002-12-19 09:40:28 +00:00
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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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1994-05-27 05:00:24 +00:00
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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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2002-12-19 09:40:28 +00:00
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The
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1994-05-27 05:00:24 +00:00
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.Fa name1
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2002-12-19 09:40:28 +00:00
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argument
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1994-05-27 05:00:24 +00:00
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may not be a directory.
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2008-04-16 13:03:12 +00:00
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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
|
2009-07-19 16:48:25 +00:00
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.It Dv AT_SYMLINK_FOLLOW
|
2008-04-16 13:03:12 +00:00
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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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2020-09-22 22:54:54 +00:00
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.It Dv AT_RESOLVE_BENEATH
|
2021-02-16 03:31:40 +00:00
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Only walk paths below the directory specified by the
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2021-03-30 21:56:28 +00:00
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.Ar fd1
|
2021-02-16 03:31:40 +00:00
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descriptor.
|
2020-09-22 22:54:54 +00:00
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See the description of the
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.Dv O_RESOLVE_BENEATH
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flag in the
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.Xr open 2
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manual page.
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2021-03-07 14:29:09 +00:00
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.It Dv AT_EMPTY_PATH
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If the
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2021-10-06 03:38:26 +00:00
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.Fa name1
|
2021-03-07 14:29:09 +00:00
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argument is an empty string, link the file referenced by the descriptor
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2021-10-06 03:38:26 +00:00
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.Fa fd1 .
|
2021-03-07 14:29:09 +00:00
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The operation requires that the calling process has the
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.Dv PRIV_VFS_FHOPEN
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privilege, effectively being executed with effective user
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.Dv root .
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2008-04-16 13:03:12 +00:00
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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.
|
1994-05-27 05:00:24 +00:00
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.Sh RETURN VALUES
|
2001-08-09 13:32:13 +00:00
|
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.Rv -std link
|
1994-05-27 05:00:24 +00:00
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.Sh ERRORS
|
2002-12-18 09:22:32 +00:00
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The
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.Fn link
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system call
|
1994-05-27 05:00:24 +00:00
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will fail and no link will be created if:
|
2000-05-04 13:09:25 +00:00
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.Bl -tag -width Er
|
1994-05-27 05:00:24 +00:00
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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.
|
1998-01-15 04:31:28 +00:00
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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
|
1999-03-05 10:39:50 +00:00
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would exceed 32767.
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1994-05-27 05:00:24 +00:00
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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
|
2006-12-09 22:56:40 +00:00
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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.
|
1994-05-27 05:00:24 +00:00
|
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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
|
|
|
|
containing the directory has been exhausted.
|
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.It Bq Er EIO
|
|
|
|
An I/O error occurred while reading from or writing to
|
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|
the file system to make the directory entry.
|
2020-03-30 21:44:00 +00:00
|
|
|
.It Bq Er EINTEGRITY
|
|
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|
Corrupted data was detected while reading from the file system.
|
1994-05-27 05:00:24 +00:00
|
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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
|
2008-04-16 13:03:12 +00:00
|
|
|
.Pp
|
|
|
|
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
|
|
|
|
.Fa fd2 ,
|
|
|
|
respectively, is neither
|
|
|
|
.Dv AT_FDCWD
|
|
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|
nor a file descriptor associated with a directory.
|
2018-10-25 22:16:34 +00:00
|
|
|
.It Bq Er ENOTCAPABLE
|
|
|
|
.Fa name1
|
|
|
|
is not strictly relative to the starting directory.
|
|
|
|
For example,
|
|
|
|
.Fa name1
|
2018-11-11 01:46:48 +00:00
|
|
|
is absolute or includes a ".." component that escapes
|
|
|
|
the directory hierarchy specified by
|
|
|
|
.Fa fd ,
|
2021-02-16 03:31:40 +00:00
|
|
|
and the process is in capability mode or the
|
|
|
|
.Dv AT_RESOLVE_BENEATH
|
|
|
|
flag was specified.
|
2008-04-16 13:03:12 +00:00
|
|
|
.El
|
1994-05-27 05:00:24 +00:00
|
|
|
.Sh SEE ALSO
|
2006-12-09 22:56:40 +00:00
|
|
|
.Xr chflags 2 ,
|
1998-01-15 04:31:28 +00:00
|
|
|
.Xr readlink 2 ,
|
1994-05-27 05:00:24 +00:00
|
|
|
.Xr symlink 2 ,
|
|
|
|
.Xr unlink 2
|
|
|
|
.Sh STANDARDS
|
1996-12-02 20:03:58 +00:00
|
|
|
The
|
|
|
|
.Fn link
|
2002-12-18 09:22:32 +00:00
|
|
|
system call is expected to conform to
|
1996-12-02 20:03:58 +00:00
|
|
|
.St -p1003.1-90 .
|
2008-04-16 13:03:12 +00:00
|
|
|
The
|
|
|
|
.Fn linkat
|
|
|
|
system call follows The Open Group Extended API Set 2 specification.
|
1996-05-24 16:32:11 +00:00
|
|
|
.Sh HISTORY
|
2002-12-18 09:22:32 +00:00
|
|
|
The
|
1996-08-29 21:24:19 +00:00
|
|
|
.Fn link
|
2002-12-18 09:22:32 +00:00
|
|
|
function appeared in
|
2017-12-01 22:26:36 +00:00
|
|
|
.At v1 .
|
2008-04-16 13:03:12 +00:00
|
|
|
The
|
|
|
|
.Fn linkat
|
|
|
|
system call appeared in
|
|
|
|
.Fx 8.0 .
|
1996-05-24 16:32:11 +00:00
|
|
|
.Pp
|
|
|
|
The
|
1996-08-22 23:31:07 +00:00
|
|
|
.Fn link
|
1996-05-24 16:32:11 +00:00
|
|
|
system call traditionally allows the super-user to link directories which
|
2004-07-02 23:52:20 +00:00
|
|
|
corrupts the file system coherency.
|
2008-04-16 13:03:12 +00:00
|
|
|
This implementation no longer permits it.
|