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
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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
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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15 .\" manual page may be incorrect or out-of-date.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
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17 .\" the use of the information contained herein. The author(s) may not
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19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
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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 2010-09-26 "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)):
51 _XOPEN_SOURCE\ >=\ 500 ||
52 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
54 || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
58 These system calls change the permissions of a file.
59 They differ only in how the file is specified:
62 changes the permissions of the file specified whose pathname is given in
64 which is dereferenced if it is a symbolic link.
67 changes the permissions of the file referred to by the open file descriptor
70 The new file permissions are specified in
72 which is a bit mask created by ORing together zero or
73 more of the following:
75 .BR S_ISUID " (04000)"
76 set-user-ID (set process effective user ID on
79 .BR S_ISGID " (02000)"
80 set-group-ID (set process effective group ID on
82 mandatory locking, as described in
84 take a new file's group from parent directory, as described in
89 .BR S_ISVTX " (01000)"
90 sticky bit (restricted deletion flag, as described in
93 .BR S_IRUSR " (00400)"
96 .BR S_IWUSR " (00200)"
99 .BR S_IXUSR " (00100)"
100 execute/search by owner ("search" applies for directories,
101 and means that entries within the directory can be accessed)
103 .BR S_IRGRP " (00040)"
106 .BR S_IWGRP " (00020)"
109 .BR S_IXGRP " (00010)"
110 execute/search by group
112 .BR S_IROTH " (00004)"
115 .BR S_IWOTH " (00002)"
118 .BR S_IXOTH " (00001)"
119 execute/search by others
121 The effective UID of the calling process must match the owner of the file,
122 or the process must be privileged (Linux: it must have the
126 If the calling process is not privileged (Linux: does not have the
128 capability), and the group of the file does not match
129 the effective group ID of the process or one of its
130 supplementary group IDs, the
132 bit will be turned off,
133 but this will not cause an error to be returned.
135 As a security measure, depending on the file system,
136 the set-user-ID and set-group-ID execution bits
137 may be turned off if a file is written.
138 (On Linux this occurs if the writing process does not have the
141 On some file systems, only the superuser can set the sticky bit,
142 which may have a special meaning.
143 For the sticky bit, and for set-user-ID and set-group-ID bits on
147 On NFS file systems, restricting the permissions will immediately influence
148 already open files, because the access control is done on the server, but
149 open files are maintained by the client.
150 Widening the permissions may be
151 delayed for other clients if attribute caching is enabled on them.
153 On success, zero is returned.
154 On error, \-1 is returned, and
156 is set appropriately.
158 Depending on the file system, other errors can be returned.
159 The more general errors for
164 Search permission is denied on a component of the path prefix.
166 .BR path_resolution (7).)
170 points outside your accessible address space.
173 An I/O error occurred.
176 Too many symbolic links were encountered in resolving
184 The file does not exist.
187 Insufficient kernel memory was available.
190 A component of the path prefix is not a directory.
193 The effective UID does not match the owner of the file,
194 and the process is not privileged (Linux: it does not have the
199 The named file resides on a read-only file system.
201 The general errors for
219 4.4BSD, SVr4, POSIX.1-2001.
226 .BR path_resolution (7)