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32 .\" @(#)chmod.2 8.1 (Berkeley) 6/4/93
33 .\" $FreeBSD: src/lib/libc/sys/chmod.2,v 1.16.2.7 2001/12/14 18:34:00 ru Exp $
34 .\" $DragonFly: src/lib/libc/sys/chmod.2,v 1.4 2006/05/26 21:39:37 swildner Exp $
43 .Nd change mode of file
49 .Fn chmod "const char *path" "mode_t mode"
51 .Fn fchmod "int fd" "mode_t mode"
53 .Fn lchmod "const char *path" "mode_t mode"
55 The file permission bits of the file named specified by
57 or referenced by the file descriptor
63 function verifies that the process owner (user) either owns
72 function follows symbolic links to operate on the target of the link
73 rather than the link itself.
77 function is similar to
79 but does not follow symbolic links.
81 A mode is created from
87 .Bd -literal -offset indent -compact
88 #define S_IRWXU 0000700 /* RWX mask for owner */
89 #define S_IRUSR 0000400 /* R for owner */
90 #define S_IWUSR 0000200 /* W for owner */
91 #define S_IXUSR 0000100 /* X for owner */
93 #define S_IRWXG 0000070 /* RWX mask for group */
94 #define S_IRGRP 0000040 /* R for group */
95 #define S_IWGRP 0000020 /* W for group */
96 #define S_IXGRP 0000010 /* X for group */
98 #define S_IRWXO 0000007 /* RWX mask for other */
99 #define S_IROTH 0000004 /* R for other */
100 #define S_IWOTH 0000002 /* W for other */
101 #define S_IXOTH 0000001 /* X for other */
103 #define S_ISUID 0004000 /* set user id on execution */
104 #define S_ISGID 0002000 /* set group id on execution */
105 #define S_ISVTX 0001000 /* sticky bit */
106 #ifndef _POSIX_SOURCE
107 #define S_ISTXT 0001000
113 VM system totally ignores the sticky bit
116 On UFS-based filesystems (FFS, MFS, LFS) the sticky
117 bit may only be set upon directories.
121 (the `sticky bit') is set on a directory,
122 an unprivileged user may not delete or rename
123 files of other users in that directory.
124 The sticky bit may be
125 set by any user on a directory which the user owns or has appropriate
127 For more details of the properties of the sticky bit, see
130 If mode ISUID (set UID) is set on a directory,
131 and the MNT_SUIDDIR option was used in the mount of the filesystem,
132 then the owner of any new files and sub-directories
133 created within this directory are set
134 to be the same as the owner of that directory.
135 If this function is enabled, new directories will inherit
136 the bit from their parents. Execute bits are removed from
137 the file, and it will not be given to root.
138 This behavior does not change the
139 requirements for the user to be allowed to write the file, but only the eventual
140 owner after it has been created.
141 Group inheritance is not affected.
143 This feature is designed for use on fileservers serving PC users via
144 ftp, SAMBA, or netatalk.
145 It provides security holes for shell users and as
146 such should not be used on shell machines, especially on home directories.
147 This option requires the SUIDDIR
148 option in the kernel to work.
149 Only UFS filesystems support this option.
150 For more details of the suiddir mount option, see
153 Writing or changing the owner of a file
154 turns off the set-user-id and set-group-id bits
155 unless the user is the super-user.
156 This makes the system somewhat more secure
157 by protecting set-user-id (set-group-id) files
158 from remaining set-user-id (set-group-id) if they are modified,
159 at the expense of a degree of compatibility.
164 will fail and the file mode will be unchanged if:
167 A component of the path prefix is not a directory.
168 .It Bq Er ENAMETOOLONG
169 A component of a pathname exceeded 255 characters,
170 or an entire path name exceeded 1023 characters.
172 The named file does not exist.
174 Search permission is denied for a component of the path prefix.
176 Too many symbolic links were encountered in translating the pathname.
178 The effective user ID does not match the owner of the file and
179 the effective user ID is not the super-user.
181 The named file resides on a read-only file system.
184 points outside the process's allocated address space.
186 An I/O error occurred while reading from or writing to the file system.
188 An attempt was made to set the sticky bit upon an executable.
195 The descriptor is not valid.
198 refers to a socket, not to a file.
200 The file resides on a read-only file system.
202 An I/O error occurred while reading from or writing to the file system.
213 function call is expected to conform to
215 except for the return of
222 function call appeared in
231 function call appeared in