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+.\" Copyright (c) 1994
+.\"	Jan-Simon Pendry
+.\"	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. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed by the University of
+.\"	California, Berkeley and its contributors.
+.\" 4. 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.
+.\"
+.\"     @(#)undelete.2	8.4 (Berkeley) 10/18/94
+.\"
+.Dd October 18, 1994
+.Dt UNDELETE 2
+.Os BSD 4
+.Sh NAME
+.Nm undelete
+.Nd attempt to recover a deleted file
+.Sh SYNOPSIS
+.Fd #include <unistd.h>
+.Ft int
+.Fn undelete "const char *path"
+.Sh DESCRIPTION
+The
+.Fn undelete
+function attempts to recover the deleted file named by
+.Fa path .
+Currently, this works only when the named object
+is a whiteout in a union filesystem.
+The system call removes the whiteout causing
+any objects in a lower layer of the
+union stack to become visible once more.
+.Pp
+Eventually, the
+.Nm undelete
+functionality may be expanded to other filesystems able to recover
+deleted files such as the log-structured filesystem.
+.Sh RETURN VALUES
+Upon successful completion, a value of 0 is returned.
+Otherwise, a value of -1 is returned and
+.Va errno
+is set to indicate the error.
+.Sh ERRORS
+The
+.Fn undelete
+succeeds unless:
+.Bl -tag -width ENAMETOOLONGAA
+.It Bq Er ENOTDIR
+A component of the path prefix is not a directory.
+.It Bq Er EINVAL
+The pathname contains a character with the high-order bit set.
+.It Bq Er ENAMETOOLONG
+A component of a pathname exceeded 255 characters,
+or an entire path name exceeded 1023 characters.
+.It Bq Er EEXIST
+The path does not reference a whiteout.
+.It Bq Er ENOENT
+The named whiteout does not exist.
+.It Bq Er EACCES
+Search permission is denied for a component of the path prefix.
+.It Bq Er EACCES
+Write permission is denied on the directory containing the name
+to be undeleted.
+.It Bq Er ELOOP
+Too many symbolic links were encountered in translating the pathname.
+.It Bq Er EPERM
+The directory containing the name is marked sticky,
+and the containing directory is not owned by the effective user ID.
+.It Bq Er EIO
+An I/O error occurred while updating the directory entry.
+.It Bq Er EROFS
+The name resides on a read-only file system.
+.It Bq Er EFAULT
+.Fa Path
+points outside the process's allocated address space.
+.El
+.Sh SEE ALSO
+.Xr unlink 2 ,
+.Xr mount_union 8
+.Sh HISTORY
+An
+.Nm undelete
+function call first appeared in 4.4BSD-Lite.