aboutsummaryrefslogtreecommitdiffstats
path: root/lib/libc/sys/chown.2
blob: 64bfdeaa961cd33e7f3de0f5f0a41196cf14f321 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
.\" 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
.\" $FreeBSD$
.\"
.Dd September 23, 2020
.Dt CHOWN 2
.Os
.Sh NAME
.Nm chown ,
.Nm fchown ,
.Nm lchown ,
.Nm fchownat
.Nd change owner and group of a file
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn chown "const char *path" "uid_t owner" "gid_t group"
.Ft int
.Fn fchown "int fd" "uid_t owner" "gid_t group"
.Ft int
.Fn lchown "const char *path" "uid_t owner" "gid_t group"
.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
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 super-user.
.Pp
The
.Fn chown
system call
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 if not executed
by the super-user.
The
.Fn chown
system call
follows symbolic links to operate on the target of the link
rather than the link itself.
.Pp
The
.Fn fchown
system call
is particularly useful when used in conjunction
with the file locking primitives (see
.Xr flock 2 ) .
.Pp
The
.Fn lchown
system call is similar to
.Fn chown
but does not follow symbolic links.
.Pp
The
.Fn fchownat
system call is equivalent to the
.Fn chown
and
.Fn lchown
except in the case where
.Fa path
specifies a relative path.
In this case the file to be changed is determined relative to the directory
associated with the file descriptor
.Fa fd
instead of the current working directory.
.Pp
Values for
.Fa flag
are constructed by a bitwise-inclusive OR of flags from the following
list, defined in
.In fcntl.h :
.Bl -tag -width indent
.It Dv AT_SYMLINK_NOFOLLOW
If
.Fa path
names a symbolic link, ownership of the symbolic link is changed.
.It Dv AT_BENEATH
Only allow to change ownership of a file which is beneath of
the topping directory.
See the description of the
.Dv O_BENEATH
flag in the
.Xr open 2
manual page.
.It Dv AT_RESOLVE_BENEATH
Only walks paths below the topping directory.
See the description of the
.Dv O_RESOLVE_BENEATH
flag in the
.Xr open 2
manual page.
.El
.Pp
If
.Fn fchownat
is passed the special value
.Dv AT_FDCWD
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
respectively, depending on whether or not the
.Dv AT_SYMLINK_NOFOLLOW
bit is set in the
.Fa flag
argument.
.Pp
One of the owner or group id's
may be left unchanged by specifying it as -1.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The
.Fn chown
and
.Fn lchown
will fail and the file 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 255 characters,
or an entire path name exceeded 1023 characters.
.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 operation would change the ownership, but the effective user ID is not the
super-user.
.It Bq Er EPERM
The named file has its immutable or append-only flag set, see the
.Xr chflags 2
manual page for more information.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EFAULT
The
.Fa path
argument
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.
.It Bq Er EINTEGRITY
Corrupted data was detected while reading from the file system.
.El
.Pp
The
.Fn fchown
system call will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument
does not refer to a valid descriptor.
.It Bq Er EINVAL
The
.Fa fd
argument
refers to a socket, not a file.
.It Bq Er EPERM
The effective user ID is not the super-user.
.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.
.It Bq Er EINTEGRITY
Corrupted data was detected while reading from the file system.
.El
.Pp
In addition to the errors specified for
.Fn chown
and
.Fn lchown ,
the
.Fn fchownat
system call may fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument does not specify an absolute path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor open for searching.
.It Bq Er EINVAL
The value of the
.Fa flag
argument is not valid.
.It Bq Er ENOTDIR
The
.Fa path
argument is not an absolute path and
.Fa fd
is neither
.Dv AT_FDCWD
nor a file descriptor associated with a directory.
.It Bq Er ENOTCAPABLE
.Fa path
is an absolute path,
or contained a ".." component leading to a
directory outside of the directory hierarchy specified by
.Fa fd ,
and the process is in capability mode.
.It Bq Er ENOTCAPABLE
The
.Dv AT_BENEATH
flag was provided to
.Fn fchownat ,
and the absolute
.Fa path
does not have its tail fully contained under the topping directory,
or the relative
.Fa path
escapes it.
.El
.Sh SEE ALSO
.Xr chgrp 1 ,
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr flock 2 ,
.Xr chown 8
.Sh STANDARDS
The
.Fn chown
system call is expected to conform to
.St -p1003.1-90 .
The
.Fn fchownat
system call follows The Open Group Extended API Set 2 specification.
.Sh HISTORY
The
.Fn chown
function appeared in
.At v1 .
The
.Fn fchown
system call appeared in
.Bx 4.2 .
.Pp
The
.Fn chown
system call was changed to follow symbolic links in
.Bx 4.4 .
The
.Fn lchown
system call was added in
.Fx 3.0
to compensate for the loss of functionality.
.Pp
The
.Fn fchownat
system call appeared in
.Fx 8.0 .