1 .\" Hey Emacs! This file is -*- nroff -*- source.
3 .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" Modified by Michael Haardt <michael@moria.de>
26 .\" Modified 1993-07-21 by Rik Faith <faith@cs.unc.edu>
27 .\" Modified 1997-01-12 by Michael Haardt
28 .\" <michael@cantor.informatik.rwth-aachen.de>: NFS details
29 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
31 .TH CHMOD 2 2008-05-26 "Linux" "Linux Programmer's Manual"
33 chmod, fchmod \- change permissions of a file
35 .B #include <sys/stat.h>
37 .BI "int chmod(const char *" path ", mode_t " mode );
39 .BI "int fchmod(int " fd ", mode_t " mode );
42 Feature Test Macro Requirements for glibc (see
43 .BR feature_test_macros (7)):
47 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
49 These system calls change the permissions of a file.
50 They differ only in how the file is specified:
53 changes the permissions of the file specified whose pathname is given in
55 which is dereferenced if it is a symbolic link.
58 changes the permissions of the file referred to by the open file descriptor
61 The new file permissions are specified in
63 which is a bit mask created by ORing together zero or
64 more of the following:
66 .BR S_ISUID " (04000)"
67 set-user-ID (set process effective user ID on
70 .BR S_ISGID " (02000)"
71 set-group-ID (set process effective group ID on
73 mandatory locking, as described in
75 take a new file's group from parent directory, as described in
80 .BR S_ISVTX " (01000)"
81 sticky bit (restricted deletion flag, as described in
84 .BR S_IRUSR " (00400)"
87 .BR S_IWUSR " (00200)"
90 .BR S_IXUSR " (00100)"
91 execute/search by owner ("search" applies for directories,
92 and means that entries within the directory can be accessed)
94 .BR S_IRGRP " (00040)"
97 .BR S_IWGRP " (00020)"
100 .BR S_IXGRP " (00010)"
101 execute/search by group
103 .BR S_IROTH " (00004)"
106 .BR S_IWOTH " (00002)"
109 .BR S_IXOTH " (00001)"
110 execute/search by others
112 The effective UID of the calling process must match the owner of the file,
113 or the process must be privileged (Linux: it must have the
117 If the calling process is not privileged (Linux: does not have the
119 capability), and the group of the file does not match
120 the effective group ID of the process or one of its
121 supplementary group IDs, the
123 bit will be turned off,
124 but this will not cause an error to be returned.
126 As a security measure, depending on the file system,
127 the set-user-ID and set-group-ID execution bits
128 may be turned off if a file is written.
129 (On Linux this occurs if the writing process does not have the
132 On some file systems, only the superuser can set the sticky bit,
133 which may have a special meaning.
134 For the sticky bit, and for set-user-ID and set-group-ID bits on
138 On NFS file systems, restricting the permissions will immediately influence
139 already open files, because the access control is done on the server, but
140 open files are maintained by the client.
141 Widening the permissions may be
142 delayed for other clients if attribute caching is enabled on them.
144 On success, zero is returned.
145 On error, \-1 is returned, and
147 is set appropriately.
149 Depending on the file system, other errors can be returned.
150 The more general errors for
155 Search permission is denied on a component of the path prefix.
157 .BR path_resolution (7).)
161 points outside your accessible address space.
164 An I/O error occurred.
167 Too many symbolic links were encountered in resolving
175 The file does not exist.
178 Insufficient kernel memory was available.
181 A component of the path prefix is not a directory.
184 The effective UID does not match the owner of the file,
185 and the process is not privileged (Linux: it does not have the
190 The named file resides on a read-only file system.
192 The general errors for
210 4.4BSD, SVr4, POSIX.1-2001.
217 .BR path_resolution (7)