224 lines
5.8 KiB
Groff
224 lines
5.8 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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.\" 4. 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 April 10, 2008
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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 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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.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 EEXIST
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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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