.\" $OpenBSD: chown.2,v 1.25 2015/01/19 15:54:11 millert Exp $ .\" $NetBSD: chown.2,v 1.10 1995/10/12 15:40:47 jtc Exp $ .\" .\" Copyright (c) 1980, 1991, 1993, 1994 .\" 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. 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. .\" .\" @(#)chown.2 8.4 (Berkeley) 4/19/94 .\" .Dd $Mdocdate: January 19 2015 $ .Dt CHOWN 2 .Os .Sh NAME .Nm chown , .Nm lchown , .Nm fchownat , .Nm fchown .Nd change owner and group of a file or link .Sh SYNOPSIS .Fd #include .Ft int .Fn chown "const char *path" "uid_t owner" "gid_t group" .Ft int .Fn lchown "const char *path" "uid_t owner" "gid_t group" .Ft int .Fn fchown "int fd" "uid_t owner" "gid_t group" .Fd #include .Fd #include .Ft int .Fn fchownat "int fd" "const char *path" "uid_t owner" "gid_t group" "int flag" .Sh DESCRIPTION The owner ID and group ID of the file (or link) named by .Fa path or referenced by .Fa fd is changed as specified by the arguments .Fa owner and .Fa group . The owner of a file may change the .Fa group to a group of which he or she is a member, but the change .Fa owner capability is restricted to the superuser. .Pp By default, .Fn chown clears the set-user-ID and set-group-ID bits on the file to prevent accidental or mischievous creation of set-user-ID and set-group-ID programs. This behaviour can be overridden by setting the .Xr sysctl 8 variable .Va fs.posix.setuid to zero. .Pp .Fn lchown operates similarly to how .Fn chown operated on older systems, and does not follow symbolic links. It allows the owner and group of a symbolic link to be set. .Pp The .Fn fchownat function is equivalent to either the .Fn chown or .Fn lchown function depending on the value of .Fa flag (see below), except that where .Fa path specifies a relative path, the file whose ownership is changed is determined relative to the directory associated with file descriptor .Fa fd instead of the current working directory. .Pp If .Fn fchownat is passed the special value .Dv AT_FDCWD (defined in .In fcntl.h ) in the .Fa fd parameter, the current working directory is used and the behavior is identical to a call to .Fn chown or .Fn lchown , depending on whether or not the .Dv AT_SYMLINK_NOFOLLOW bit is set in .Fa flag . .Pp The .Fa flag argument is the bitwise OR of zero or more of the following values: .Pp .Bl -tag -width AT_SYMLINK_NOFOLLOW -offset indent -compact .It Dv AT_SYMLINK_NOFOLLOW If .Fa path names a symbolic link, then the ownership of the symbolic link is changed. .El .Pp .Fn fchown is particularly useful when used in conjunction with the file locking primitives (see .Xr flock 2 ) . .Pp One of the owner or group IDs may be left unchanged by specifying it as \-1. .Sh RETURN VALUES .Rv -std .Sh ERRORS .Fn chown , .Fn lchown , and .Fn fchownat will fail and the file or link will be unchanged if: .Bl -tag -width Er .It Bq Er ENOTDIR A component of the path prefix is not a directory. .It Bq Er ENAMETOOLONG A component of a pathname exceeded .Dv NAME_MAX characters, or an entire pathname (including the terminating NUL) exceeded .Dv PATH_MAX bytes. .It Bq Er ENOENT The named file does not exist. .It Bq Er EACCES Search permission is denied for a component of the path prefix. .It Bq Er ELOOP Too many symbolic links were encountered in translating the pathname. .It Bq Er EPERM The effective user ID is not the superuser. .It Bq Er EROFS The named file resides on a read-only file system. .It Bq Er EFAULT .Fa path points outside the process's allocated address space. .It Bq Er EIO An I/O error occurred while reading from or writing to the file system. .El .Pp Additionally, .Fn fchownat will fail if: .Bl -tag -width Er .It Bq Er EINVAL The value of the .Fa flag argument was neither zero nor .Dv AT_SYMLINK_NOFOLLOW . .It Bq Er EBADF The .Fa path argument specifies a relative path and the .Fa fd argument is neither .Dv AT_FDCWD nor a valid file descriptor. .It Bq Er ENOTDIR The .Fa path argument specifies a relative path and the .Fa fd argument is a valid file descriptor but it does not reference a directory. .It Bq Er EACCES The .Fa path argument specifies a relative path but search permission is denied for the directory which the .Fa fd file descriptor references. .El .Pp .Fn fchown will fail if: .Bl -tag -width Er .It Bq Er EBADF .Fa fd does not refer to a valid descriptor. .It Bq Er EINVAL .Fa fd refers to a socket, not a file. .It Bq Er EPERM The effective user ID is not the superuser. .It Bq Er EROFS The named file resides on a read-only file system. .It Bq Er EIO An I/O error occurred while reading from or writing to the file system. .El .Sh SEE ALSO .Xr chgrp 1 , .Xr chmod 2 , .Xr flock 2 , .Xr chown 8 .Sh STANDARDS The .Fn chown , .Fn fchown , .Fn fchownat , and .Fn lchown functions are expected to conform to .St -p1003.1-2008 . .Sh HISTORY The .Fn chown system call first appeared in .At v1 . Since .At v6 it supports changing the group as well, and in .At v7 .Fa group was made a separate argument. .Pp The .Fn fchown system call first appeared in .Bx 4.1c . .Pp The .Fn chown and .Fn fchown system calls were changed to follow symbolic links in .Bx 4.4 ; therefore, and for compatibility with .At V.4 , the .Fn lchown system call was added to .Ox 2.1 . .Pp The .Fn fchownat system call has been available since .Ox 5.0 .