509124b626
It is currently allowed to fchownat(2), fchmodat(2), fchflagsat(2), utimensat(2), fstatat(2), and linkat(2). For linkat(2), PRIV_VFS_FHOPEN privilege is required to exercise the flag. It allows to link any open file. Requested by: trasz Tested by: pho, trasz Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D29111
302 lines
7.2 KiB
Groff
302 lines
7.2 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993, 1994
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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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.\" @(#)chown.2 8.4 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd March 30, 2021
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.Dt CHOWN 2
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.Os
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.Sh NAME
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.Nm chown ,
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.Nm fchown ,
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.Nm lchown ,
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.Nm fchownat
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.Nd change owner and group of a file
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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 chown "const char *path" "uid_t owner" "gid_t group"
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.Ft int
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.Fn fchown "int fd" "uid_t owner" "gid_t group"
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.Ft int
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.Fn lchown "const char *path" "uid_t owner" "gid_t group"
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.Ft int
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.Fn fchownat "int fd" "const char *path" "uid_t owner" "gid_t group" "int flag"
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.Sh DESCRIPTION
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The owner ID and group ID of the file
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named by
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.Fa path
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or referenced by
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.Fa fd
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is changed as specified by the arguments
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.Fa owner
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and
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.Fa group .
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The owner of a file may change the
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.Fa group
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to a group of which
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he or she is a member,
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but the change
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.Fa owner
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capability is restricted to the super-user.
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.Pp
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The
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.Fn chown
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system call
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clears the set-user-id and set-group-id bits
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on the file
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to prevent accidental or mischievous creation of
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set-user-id and set-group-id programs if not executed
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by the super-user.
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The
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.Fn chown
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system call
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follows symbolic links to operate on the target of the link
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rather than the link itself.
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.Pp
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The
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.Fn fchown
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system call
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is particularly useful when used in conjunction
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with the file locking primitives (see
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.Xr flock 2 ) .
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.Pp
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The
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.Fn lchown
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system call is similar to
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.Fn chown
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but does not follow symbolic links.
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.Pp
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The
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.Fn fchownat
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system call is equivalent to the
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.Fn chown
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and
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.Fn lchown
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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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.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
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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, ownership of the symbolic link is changed.
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.It Dv AT_RESOLVE_BENEATH
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Only walk paths below the directory specified by the
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.Ar fd
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descriptor.
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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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.It Dv AT_EMPTY_PATH
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If the
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.Fa path
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argument is an empty string, operate on the file or directory
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referenced by the descriptor
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.Fa fd .
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If
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.Fa fd
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is equal to
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.Dv AT_FDCWD ,
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operate on the current working directory.
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.El
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.Pp
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If
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.Fn fchownat
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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 identical
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to a call to
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.Fn chown
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or
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.Fn lchown
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respectively, depending on whether or not the
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.Dv AT_SYMLINK_NOFOLLOW
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bit is set in the
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.Fa flag
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argument.
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.Pp
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One of the owner or group id's
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may be left unchanged by specifying it as -1.
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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 chown
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and
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.Fn lchown
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will fail and the file will be unchanged 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 operation would change the ownership, but the effective user ID is not the
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super-user.
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.It Bq Er EPERM
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The named file 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 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 I/O 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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.El
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.Pp
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The
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.Fn fchown
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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
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.Fa fd
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argument
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does not refer to a valid descriptor.
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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 a file.
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.It Bq Er EPERM
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The effective user ID is not the super-user.
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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 EIO
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An I/O 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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.El
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.Pp
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In addition to the errors specified for
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.Fn chown
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and
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.Fn lchown ,
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the
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.Fn fchownat
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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 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 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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.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 or the
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.Dv AT_RESOLVE_BENEATH
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flag was specified.
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.El
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.Sh SEE ALSO
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.Xr chgrp 1 ,
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.Xr chflags 2 ,
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.Xr chmod 2 ,
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.Xr flock 2 ,
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.Xr chown 8
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.Sh STANDARDS
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The
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.Fn chown
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system call is expected to conform to
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.St -p1003.1-90 .
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The
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.Fn fchownat
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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 chown
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function appeared in
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.At v1 .
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The
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.Fn fchown
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system call appeared in
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.Bx 4.2 .
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.Pp
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The
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.Fn chown
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system call was changed to follow symbolic links in
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.Bx 4.4 .
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The
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.Fn lchown
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system call was added in
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.Fx 3.0
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to compensate for the loss of functionality.
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.Pp
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The
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.Fn fchownat
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system call appeared in
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.Fx 8.0 .
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