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
229 lines
6.0 KiB
Groff
229 lines
6.0 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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.\" @(#)unlink.2 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd July 28, 2015
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.Dt UNLINK 2
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.Os
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.Sh NAME
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.Nm unlink ,
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.Nm unlinkat
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.Nd remove directory entry
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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 unlink "const char *path"
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.Ft int
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.Fn unlinkat "int fd" "const char *path" "int flag"
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.Sh DESCRIPTION
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The
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.Fn unlink
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system call
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removes the link named by
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.Fa path
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from its directory and decrements the link count of the
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file which was referenced by the link.
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If that decrement reduces the link count of the file
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to zero,
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and no process has the file open, then
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all resources associated with the file are reclaimed.
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If one or more process have the file open when the last link is removed,
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the link is removed, but the removal of the file is delayed until
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all references to it have been closed.
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The
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.Fa path
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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 unlinkat
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system call is equivalent to
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.Fn unlink
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or
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.Fn rmdir
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except in the case where
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.Fa path
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specifies a relative path.
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In this case the directory entry to be removed is determined
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relative to the directory associated with the file descriptor
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.Fa fd
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instead of the current working directory.
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.Pp
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The values for
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.Fa flag
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are constructed by a bitwise-inclusive OR of flags from the following list,
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defined in
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.In fcntl.h :
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.Bl -tag -width indent
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.It Dv AT_REMOVEDIR
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Remove the directory entry specified by
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.Fa fd
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and
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.Fa path
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as a directory, not a normal file.
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.El
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.Pp
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If
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.Fn unlinkat
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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 fd
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parameter, the current working directory is used and the behavior is
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identical to a call to
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.Fa unlink
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or
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.Fa rmdir
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respectively, depending on whether or not the
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.Dv AT_REMOVEDIR
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bit is set in flag.
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.Sh RETURN VALUES
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.Rv -std unlink
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.Sh ERRORS
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The
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.Fn unlink
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succeeds unless:
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.Bl -tag -width Er
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er EISDIR
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The named file is a directory.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or an entire path name exceeded 1023 characters.
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.It Bq Er ENOENT
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The named file does not exist.
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.It Bq Er EACCES
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Search permission is denied for a component of the path prefix.
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.It Bq Er EACCES
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Write permission is denied on the directory containing the link
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to be removed.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er EPERM
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The named file is a directory.
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.It Bq Er EPERM
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The named file has its immutable, undeletable 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 named file has its immutable or append-only flag
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set.
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.It Bq Er EPERM
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The directory containing the file is marked sticky,
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and neither the containing directory nor the file to be removed
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are owned by the effective user ID.
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.It Bq Er EIO
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An I/O error occurred while deleting the directory entry
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or deallocating the inode.
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.It Bq Er EROFS
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The named file resides on a read-only file system.
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.It Bq Er EFAULT
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The
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.Fa path
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argument
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points outside the process's allocated address space.
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.It Bq Er ENOSPC
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On file systems supporting copy-on-write or snapshots, there was not enough
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free space to record metadata for the delete operation of the file.
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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 unlink ,
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the
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.Fn unlinkat
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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 path
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argument does not specify an absolute path and the
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.Fa fd
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argument 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 ENOTEMPTY
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The
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.Fa flag
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parameter has the
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.Dv AT_REMOVEDIR
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bit set and the
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.Fa path
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argument names a directory that is not an empty directory,
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or there are hard links to the directory other than dot or
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a single entry in dot-dot.
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.It Bq Er ENOTDIR
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The
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.Fa flag
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parameter has the
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.Dv AT_REMOVEDIR
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bit set and
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.Fa path
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does not name a directory.
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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 path
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argument is not an absolute path and
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.Fa fd
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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 close 2 ,
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.Xr link 2 ,
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.Xr rmdir 2 ,
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.Xr symlink 7
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.Sh STANDARDS
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The
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.Fn unlinkat
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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 unlink
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function appeared in
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.At v6 .
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The
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.Fn unlinkat
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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 unlink
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system call traditionally allows the super-user to unlink directories which
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can damage the file system integrity.
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This implementation no longer permits it.
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