1.\" Copyright (c) 1980, 1991, 1993, 1994 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)chown.2 8.4 (Berkeley) 4/19/94 29.\" $FreeBSD: src/lib/libc/sys/chown.2,v 1.12.2.6 2001/12/14 18:34:00 ru Exp $ 30.\" $DragonFly: src/lib/libc/sys/chown.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 31.\" 32.Dd August 9, 2009 33.Dt CHOWN 2 34.Os 35.Sh NAME 36.Nm chown , 37.Nm fchown , 38.Nm lchown , 39.Nm fchownat 40.Nd change owner and group of a file 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In unistd.h 45.Ft int 46.Fn chown "const char *path" "uid_t owner" "gid_t group" 47.Ft int 48.Fn fchown "int fd" "uid_t owner" "gid_t group" 49.Ft int 50.Fn lchown "const char *path" "uid_t owner" "gid_t group" 51.Ft int 52.Fn fchownat "int dirfd" "const char *path" "uid_t owner" "gid_t group" "int flags" 53.Sh DESCRIPTION 54The owner ID and group ID of the file 55named by 56.Fa path 57or referenced by 58.Fa fd 59is changed as specified by the arguments 60.Fa owner 61and 62.Fa group . 63The owner of a file may change the 64.Fa group 65to a group of which 66he or she is a member, 67but the change 68.Fa owner 69capability is restricted to the super-user. 70.Pp 71.Fn Chown 72clears the set-user-id and set-group-id bits 73on the file 74to prevent accidental or mischievous creation of 75set-user-id and set-group-id programs if not executed 76by the super-user. 77.Fn chown 78follows symbolic links to operate on the target of the link 79rather than the link itself. 80.Pp 81.Fn Fchown 82is particularly useful when used in conjunction 83with the file locking primitives (see 84.Xr flock 2 ) . 85.Pp 86.Fn Lchown 87is similar to 88.Fn chown 89but does not follow symbolic links. 90.Pp 91One of the owner or group id's 92may be left unchanged by specifying it as -1. 93.Pp 94The 95.Fn fchownat 96function is equivalent to the 97.Fn chown 98or 99.Fn lchown 100functions except in the case where the 101.Fa path 102specifies a relative path. 103In this case the file to be opened is determined relative to the directory 104associated with the file descriptor 105.Fa dirfd 106instead of the current working directory. 107If 108.Fn fchownat 109is passed the special value 110.Dv AT_FDCWD 111in the 112.Fa dirfd 113parameter, the current working directory is used 114and the behavior is identical to a call to 115.Fn chown 116or 117.Fn lchown . 118.Pp 119The values for the 120.Fa flags 121are constructed by a bitwise-inclusive OR of flags from the following list, 122defined in 123.In fcntl.h : 124.Bl -tag -width indent 125.It Dv AT_SYMLINK_NOFOLLOW 126If 127.Fa path 128names a symbolic link, the mode of the symbolic link is changed. 129.El 130.Sh RETURN VALUES 131.Rv -std 132.Sh ERRORS 133.Fn Chown , 134.Fn lchown 135and 136.Fn fchownat 137will fail and the file will be unchanged if: 138.Bl -tag -width Er 139.It Bq Er ENOTDIR 140A component of the path prefix or 141.Fa dirfd 142is not a directory. 143.It Bq Er ENAMETOOLONG 144A component of a pathname exceeded 255 characters, 145or an entire path name exceeded 1023 characters. 146.It Bq Er ENOENT 147The named file does not exist. 148.It Bq Er EACCES 149Search permission is denied for a component of the path prefix. 150.It Bq Er ELOOP 151Too many symbolic links were encountered in translating the pathname. 152.It Bq Er EPERM 153The effective user ID is not the super-user. 154.It Bq Er EROFS 155The named file resides on a read-only file system. 156.It Bq Er EFAULT 157.Fa Path 158points outside the process's allocated address space. 159.It Bq Er EIO 160An I/O error occurred while reading from or writing to the file system. 161.El 162.Pp 163.Fn Fchown 164will fail if: 165.Bl -tag -width Er 166.It Bq Er EBADF 167.Fa fd 168does not refer to a valid descriptor. 169.It Bq Er EINVAL 170.Fa fd 171refers to a socket, not a file. 172.It Bq Er EPERM 173The effective user ID is not the super-user. 174.It Bq Er EROFS 175The named file resides on a read-only file system. 176.It Bq Er EIO 177An I/O error occurred while reading from or writing to the file system. 178.El 179.Sh SEE ALSO 180.Xr chgrp 1 , 181.Xr chmod 2 , 182.Xr flock 2 , 183.Xr chown 8 184.Sh STANDARDS 185The 186.Fn chown 187function call is expected to conform to 188.St -p1003.1-90 . 189.Sh HISTORY 190A 191.Fn chown 192function call appeared in 193.At v7 . 194The 195.Fn fchown 196function call 197appeared in 198.Bx 4.2 . 199.Pp 200The 201.Fn chown 202function was changed to follow symbolic links in 203.Bx 4.4 . 204The 205.Fn lchown 206function was added in 207.Fx 3.0 208to compensate for the loss of functionality. 209.Pp 210The 211.Fn fchownat 212system call appeared in 213.Dx 2.3 . 214