1f305be431
PR: 248335 Reviewed by: markj Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D25886
364 lines
9.9 KiB
Groff
364 lines
9.9 KiB
Groff
.\" Copyright (c) 1989, 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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.\" @(#)chflags.2 8.3 (Berkeley) 5/2/95
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.\" $FreeBSD$
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.\"
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.Dd September 23, 2020
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.Dt CHFLAGS 2
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.Os
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.Sh NAME
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.Nm chflags ,
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.Nm lchflags ,
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.Nm fchflags ,
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.Nm chflagsat
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.Nd set file flags
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/stat.h
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.In unistd.h
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.Ft int
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.Fn chflags "const char *path" "unsigned long flags"
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.Ft int
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.Fn lchflags "const char *path" "unsigned long flags"
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.Ft int
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.Fn fchflags "int fd" "unsigned long flags"
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.Ft int
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.Fn chflagsat "int fd" "const char *path" "unsigned long flags" "int atflag"
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.Sh DESCRIPTION
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The file whose name
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is given by
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.Fa path
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or referenced by the descriptor
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.Fa fd
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has its flags changed to
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.Fa flags .
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.Pp
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The
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.Fn lchflags
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system call is like
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.Fn chflags
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except in the case where the named file is a symbolic link,
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in which case
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.Fn lchflags
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will change the flags of the link itself,
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rather than the file it points to.
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.Pp
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The
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.Fn chflagsat
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is equivalent to either
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.Fn chflags
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or
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.Fn lchflags
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depending on the
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.Fa atflag
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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 file to be changed is determined relative to the directory
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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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The values for the
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.Fa atflag
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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_SYMLINK_NOFOLLOW
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If
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.Fa path
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names a symbolic link, then the flags of the symbolic link are changed.
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.It Dv AT_BENEATH
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Only allow to change flags for a file which is beneath of
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the topping directory.
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See the description of the
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.Dv O_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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.It Dv AT_RESOLVE_BENEATH
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Only walks paths below the topping directory.
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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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.El
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.Pp
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If
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.Fn chflagsat
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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.
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If also
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.Fa atflag
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is zero, the behavior is identical to a call to
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.Fn chflags .
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.Pp
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The flags specified are formed by
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.Em or Ns 'ing
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the following values
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.Pp
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.Bl -tag -width ".Dv SF_IMMUTABLE" -compact -offset indent
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.It Dv SF_APPEND
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The file may only be appended to.
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.It Dv SF_ARCHIVED
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The file has been archived.
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This flag means the opposite of the DOS, Windows and CIFS
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FILE_ATTRIBUTE_ARCHIVE attribute.
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This flag has been deprecated, and may be removed in a future release.
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.It Dv SF_IMMUTABLE
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The file may not be changed.
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.It Dv SF_NOUNLINK
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The file may not be renamed or deleted.
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.It Dv SF_SNAPSHOT
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The file is a snapshot file.
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.It Dv UF_APPEND
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The file may only be appended to.
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.It Dv UF_ARCHIVE
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The file needs to be archived.
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This flag has the same meaning as the DOS, Windows and CIFS
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FILE_ATTRIBUTE_ARCHIVE attribute.
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Filesystems in FreeBSD may or may not have special handling for this flag.
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For instance, ZFS tracks changes to files and will set this bit when a
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file is updated.
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UFS only stores the flag, and relies on the application to change it when
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needed.
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.It Dv UF_HIDDEN
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The file may be hidden from directory listings at the application's
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discretion.
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The file has the DOS, Windows and CIFS FILE_ATTRIBUTE_HIDDEN attribute.
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.It Dv UF_IMMUTABLE
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The file may not be changed.
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.It Dv UF_NODUMP
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Do not dump the file.
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.It Dv UF_NOUNLINK
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The file may not be renamed or deleted.
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.It Dv UF_OFFLINE
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The file is offline, or has the Windows and CIFS FILE_ATTRIBUTE_OFFLINE
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attribute.
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Filesystems in FreeBSD store and display this flag, but do not provide any
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special handling when it is set.
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.It Dv UF_OPAQUE
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The directory is opaque when viewed through a union stack.
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.It Dv UF_READONLY
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The file is read only, and may not be written or appended.
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Filesystems may use this flag to maintain compatibility with the DOS, Windows
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and CIFS FILE_ATTRIBUTE_READONLY attribute.
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.It Dv UF_REPARSE
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The file contains a Windows reparse point and has the Windows and CIFS
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FILE_ATTRIBUTE_REPARSE_POINT attribute.
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.It Dv UF_SPARSE
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The file has the Windows FILE_ATTRIBUTE_SPARSE_FILE attribute.
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This may also be used by a filesystem to indicate a sparse file.
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.It Dv UF_SYSTEM
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The file has the DOS, Windows and CIFS FILE_ATTRIBUTE_SYSTEM attribute.
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Filesystems in FreeBSD may store and display this flag, but do not provide
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any special handling when it is set.
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.El
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.Pp
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If one of
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.Dv SF_IMMUTABLE , SF_APPEND ,
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or
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.Dv SF_NOUNLINK
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is set a non-super-user cannot change any flags and even the super-user
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can change flags only if securelevel is 0.
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(See
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.Xr init 8
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for details.)
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.Pp
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The
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.Dv UF_IMMUTABLE , UF_APPEND , UF_NOUNLINK , UF_NODUMP ,
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and
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.Dv UF_OPAQUE
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flags may be set or unset by either the owner of a file or the super-user.
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.Pp
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The
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.Dv SF_IMMUTABLE , SF_APPEND , SF_NOUNLINK ,
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and
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.Dv SF_ARCHIVED
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flags may only be set or unset by the super-user.
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Attempts to toggle these flags by non-super-users are rejected.
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These flags may be set at any time, but normally may only be unset when
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the system is in single-user mode.
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(See
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.Xr init 8
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for details.)
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.Pp
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The implementation of all flags is filesystem-dependent.
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See the description of the
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.Dv UF_ARCHIVE
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flag above for one example of the differences in behavior.
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Care should be exercised when writing applications to account for
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support or lack of support of these flags in various filesystems.
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.Pp
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The
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.Dv SF_SNAPSHOT
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flag is maintained by the system and cannot be toggled.
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.Sh RETURN VALUES
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.Rv -std
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.Sh ERRORS
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The
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.Fn chflags
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system call will fail if:
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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 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 effective user ID does not match the owner of the file and
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the effective user ID is not the super-user.
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.It Bq Er EPERM
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One of
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.Dv SF_IMMUTABLE , SF_APPEND ,
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or
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.Dv SF_NOUNLINK
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is set and the user is either not the super-user or
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securelevel is greater than 0.
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.It Bq Er EPERM
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A non-super-user attempted to toggle one of
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.Dv SF_ARCHIVED , SF_IMMUTABLE , SF_APPEND ,
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or
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.Dv SF_NOUNLINK .
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.It Bq Er EPERM
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An attempt was made to toggle the
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.Dv SF_SNAPSHOT
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flag.
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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 EIO
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An
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.Tn I/O
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error occurred while reading from or writing to the file system.
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.It Bq Er EINTEGRITY
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Corrupted data was detected while reading from the file system.
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.It Bq Er EOPNOTSUPP
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The underlying file system does not support file flags, or
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does not support all of the flags set in
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.Fa flags .
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.El
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.Pp
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The
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.Fn fchflags
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system call will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The descriptor is not valid.
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.It Bq Er EINVAL
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The
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.Fa fd
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argument
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refers to a socket, not to a file.
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.It Bq Er EPERM
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The effective user ID does not match the owner of the file and
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the effective user ID is not the super-user.
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.It Bq Er EPERM
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One of
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.Dv SF_IMMUTABLE , SF_APPEND ,
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or
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.Dv SF_NOUNLINK
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is set and the user is either not the super-user or
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securelevel is greater than 0.
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.It Bq Er EPERM
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A non-super-user attempted to toggle one of
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.Dv SF_ARCHIVED , SF_IMMUTABLE , SF_APPEND ,
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or
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.Dv SF_NOUNLINK .
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.It Bq Er EPERM
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An attempt was made to toggle the
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.Dv SF_SNAPSHOT
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flag.
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.It Bq Er EROFS
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The file resides on a read-only file system.
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.It Bq Er EIO
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An
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.Tn I/O
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error occurred while reading from or writing to the file system.
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.It Bq Er EINTEGRITY
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Corrupted data was detected while reading from the file system.
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.It Bq Er EOPNOTSUPP
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The underlying file system does not support file flags, or
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does not support all of the flags set in
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.Fa flags .
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.It Bq Er ENOTCAPABLE
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.Fa path
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is an absolute path,
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or contained a ".." component leading to a
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directory outside of the directory hierarchy specified by
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.Fa fd ,
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and the process is in capability mode.
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.It Bq Er ENOTCAPABLE
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The
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.Dv AT_BENEATH
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flag was provided to
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.Fn chflagsat ,
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and the absolute
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.Fa path
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does not have its tail fully contained under the topping directory,
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or the relative
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.Fa path
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escapes it.
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.El
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.Sh SEE ALSO
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.Xr chflags 1 ,
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.Xr fflagstostr 3 ,
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.Xr strtofflags 3 ,
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.Xr init 8 ,
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.Xr mount_unionfs 8
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.Sh HISTORY
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The
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.Fn chflags
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and
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.Fn fchflags
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system calls first appeared in
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.Bx 4.4 .
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The
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.Fn lchflags
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system call first appeared in
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.Fx 5.0 .
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The
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.Fn chflagsat
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system call first appeared in
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.Fx 10.0 .
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