1 .\" Hey Emacs! This file is -*- nroff -*- source.
3 .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
4 .\" and Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl)
5 .\" and Copyright (c) 2007, 2008 Michael Kerrisk <mtk.manpages@gmail.com>
7 .\" Permission is granted to make and distribute verbatim copies of this
8 .\" manual provided the copyright notice and this permission notice are
9 .\" preserved on all copies.
11 .\" Permission is granted to copy and distribute modified versions of this
12 .\" manual under the conditions for verbatim copying, provided that the
13 .\" entire resulting derived work is distributed under the terms of a
14 .\" permission notice identical to this one.
16 .\" Since the Linux kernel and libraries are constantly changing, this
17 .\" manual page may be incorrect or out-of-date. The author(s) assume no
18 .\" responsibility for errors or omissions, or for damages resulting from
19 .\" the use of the information contained herein. The author(s) may not
20 .\" have taken the same level of care in the production of this manual,
21 .\" which is licensed free of charge, as they might when working
24 .\" Formatted or processed versions of this manual, if unaccompanied by
25 .\" the source, must acknowledge the copyright and authors of this work.
27 .\" Modified by Michael Haardt <michael@moria.de>
28 .\" Modified 1993-07-21 by Rik Faith <faith@cs.unc.edu>
29 .\" Modified 1996-07-09 by Andries Brouwer <aeb@cwi.nl>
30 .\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
31 .\" Modified 1997-05-18 by Michael Haardt <michael@cantor.informatik.rwth-aachen.de>
32 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
33 .\" 2007-07-08, mtk, added an example program; updated SYNOPSIS
34 .\" 2008-05-08, mtk, Describe rules governing ownership of new files
35 .\" (bsdgroups versus sysvgroups, and the effect of the parent
36 .\" directory's set-group-ID permission bit).
38 .TH CHOWN 2 2008-06-16 "Linux" "Linux Programmer's Manual"
40 chown, fchown, lchown \- change ownership of a file
42 .B #include <unistd.h>
44 .BI "int chown(const char *" path ", uid_t " owner ", gid_t " group );
46 .BI "int fchown(int " fd ", uid_t " owner ", gid_t " group );
48 .BI "int lchown(const char *" path ", uid_t " owner ", gid_t " group );
51 Feature Test Macro Requirements for glibc (see
52 .BR feature_test_macros (7)):
57 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
59 These system calls change the owner and group of a file.
60 The differ only in how the file is specified:
63 changes the ownership of the file specified by
65 which is dereferenced if it is a symbolic link.
68 changes the ownership of the file referred to by the open file descriptor
74 but does not dereference symbolic links.
76 Only a privileged process (Linux: one with the
78 capability) may change the owner of a file.
79 The owner of a file may change the group of the file
80 to any group of which that owner is a member.
81 A privileged process (Linux: with
83 may change the group arbitrarily.
89 is specified as \-1, then that ID is not changed.
91 When the owner or group of an executable file are
92 changed by an unprivileged user the
96 mode bits are cleared.
97 POSIX does not specify whether
98 this also should happen when root does the
100 the Linux behavior depends on the kernel version.
101 .\" In Linux 2.0 kernels, superuser was like everyone else
102 .\" In 2.2, up to 2.2.12, these bits were not cleared for superuser.
103 .\" Since 2.2.13, superuser is once more like everyone else.
104 In case of a non-group-executable file (i.e., one for which the
108 bit indicates mandatory locking, and is not cleared by a
111 On success, zero is returned.
112 On error, \-1 is returned, and
114 is set appropriately.
116 Depending on the file system, other errors can be returned.
117 The more general errors for
122 Search permission is denied on a component of the path prefix.
124 .BR path_resolution (7).)
128 points outside your accessible address space.
131 Too many symbolic links were encountered in resolving
139 The file does not exist.
142 Insufficient kernel memory was available.
145 A component of the path prefix is not a directory.
148 The calling process did not have the required permissions
149 (see above) to change owner and/or group.
152 The named file resides on a read-only file system.
154 The general errors for
159 The descriptor is not valid.
162 A low-level I/O error occurred while modifying the inode.
173 4.4BSD, SVr4, POSIX.1-2001.
175 The 4.4BSD version can only be
176 used by the superuser (that is, ordinary users cannot give away files).
178 .\" SVr4 documents EINVAL, EINTR, ENOLINK and EMULTIHOP returns, but no
179 .\" ENOMEM. POSIX.1 does not document ENOMEM or ELOOP error conditions.
181 .\" SVr4 documents additional EINVAL, EIO, EINTR, and ENOLINK
182 .\" error conditions.
184 When a new file is created (by, for example,
188 its owner is made the same as the file system user ID of the
190 The group of the file depends on a range of factors,
191 including the type of file system,
192 the options used to mount the file system,
193 and whether or not the set-group-ID permission bit is enabled
194 on the parent directory.
195 If the file system supports the
198 .IR "\-o\ bsdgroups" )
202 .IR "\-o\ sysvgroups" )
204 options, then the rules are as follows:
206 If the file system is mounted with
208 then the group of a new file is made
209 the same as that of the parent directory.
211 If the file system is mounted with
213 and the set-group-ID bit is disabled on the parent directory,
214 then the group of a new file is made the same as the
215 process's file system GID.
217 If the file system is mounted with
219 and the set-group-ID bit is enabled on the parent directory,
220 then the group of a new file is made
221 the same as that of the parent directory.
228 mount options are supported by ext2, ext3, ext4, and XFS.
229 File systems that don't support these mount options follow the
235 semantics are deliberately violated on NFS file systems
236 which have UID mapping enabled.
237 Additionally, the semantics of all system
238 calls which access the file contents are violated, because
240 may cause immediate access revocation on already open files.
242 caching may lead to a delay between the time where ownership have
243 been changed to allow access for a user and the time where the file can
244 actually be accessed by the user on other clients.
246 In versions of Linux prior to 2.1.81 (and distinct from 2.1.46),
248 did not follow symbolic links.
251 does follow symbolic links, and there is a new system call
253 that does not follow symbolic links.
254 Since Linux 2.1.86, this new call (that has the same semantics
257 has got the same syscall number, and
259 got the newly introduced number.
262 The following program changes the ownership of the file named in
263 its second command-line argument to the value specified in its
264 first command-line argument.
265 The new owner can be specified either as a numeric user ID,
266 or as a username (which is converted to a user ID by using
268 to perform a lookup in the system password file).
277 main(int argc, char *argv[])
283 if (argc != 3 || argv[1][0] == \(aq\\0\(aq) {
284 fprintf(stderr, "%s <owner> <file>\\n", argv[0]);
288 uid = strtol(argv[1], &endptr, 10); /* Allow a numeric string */
290 if (*endptr != \(aq\\0\(aq) { /* Was not pure numeric string */
291 pwd = getpwnam(argv[1]); /* Try getting UID for username */
300 if (chown(argv[2], uid, \-1) == \-1) {
312 .BR path_resolution (7),