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28 .\" @(#)chmod.2 8.1 (Berkeley) 6/4/93
38 .Nd change mode of file
44 .Fn chmod "const char *path" "mode_t mode"
46 .Fn fchmod "int fd" "mode_t mode"
48 .Fn lchmod "const char *path" "mode_t mode"
50 The file permission bits of the file named specified by
52 or referenced by the file descriptor
58 system call verifies that the process owner (user) either owns
67 system call follows symbolic links to operate on the target of the link
68 rather than the link itself.
72 system call is similar to
74 but does not follow symbolic links.
76 A mode is created from
82 .Bd -literal -offset indent -compact
83 #define S_IRWXU 0000700 /* RWX mask for owner */
84 #define S_IRUSR 0000400 /* R for owner */
85 #define S_IWUSR 0000200 /* W for owner */
86 #define S_IXUSR 0000100 /* X for owner */
88 #define S_IRWXG 0000070 /* RWX mask for group */
89 #define S_IRGRP 0000040 /* R for group */
90 #define S_IWGRP 0000020 /* W for group */
91 #define S_IXGRP 0000010 /* X for group */
93 #define S_IRWXO 0000007 /* RWX mask for other */
94 #define S_IROTH 0000004 /* R for other */
95 #define S_IWOTH 0000002 /* W for other */
96 #define S_IXOTH 0000001 /* X for other */
98 #define S_ISUID 0004000 /* set user id on execution */
99 #define S_ISGID 0002000 /* set group id on execution */
100 #ifndef __BSD_VISIBLE
101 #define S_ISTXT 0001000 /* sticky bit */
107 VM system totally ignores the sticky bit
110 On UFS-based file systems (FFS, LFS) the sticky
111 bit may only be set upon directories.
115 (the `sticky bit') is set on a directory,
116 an unprivileged user may not delete or rename
117 files of other users in that directory.
118 The sticky bit may be
119 set by any user on a directory which the user owns or has appropriate
121 For more details of the properties of the sticky bit, see
124 If mode ISUID (set UID) is set on a directory,
125 and the MNT_SUIDDIR option was used in the mount of the file system,
126 then the owner of any new files and sub-directories
127 created within this directory are set
128 to be the same as the owner of that directory.
129 If this function is enabled, new directories will inherit
130 the bit from their parents.
131 Execute bits are removed from
132 the file, and it will not be given to root.
133 This behavior does not change the
134 requirements for the user to be allowed to write the file, but only the eventual
135 owner after it has been created.
136 Group inheritance is not affected.
138 This feature is designed for use on fileservers serving PC users via
139 ftp, SAMBA, or netatalk.
140 It provides security holes for shell users and as
141 such should not be used on shell machines, especially on home directories.
142 This option requires the SUIDDIR
143 option in the kernel to work.
144 Only UFS file systems support this option.
145 For more details of the suiddir mount option, see
148 Writing or changing the owner of a file
149 turns off the set-user-id and set-group-id bits
150 unless the user is the super-user.
151 This makes the system somewhat more secure
152 by protecting set-user-id (set-group-id) files
153 from remaining set-user-id (set-group-id) if they are modified,
154 at the expense of a degree of compatibility.
161 will fail and the file mode will be unchanged if:
164 A component of the path prefix is not a directory.
165 .It Bq Er ENAMETOOLONG
166 A component of a pathname exceeded 255 characters,
167 or an entire path name exceeded 1023 characters.
169 The named file does not exist.
171 Search permission is denied for a component of the path prefix.
173 Too many symbolic links were encountered in translating the pathname.
175 The effective user ID does not match the owner of the file and
176 the effective user ID is not the super-user.
178 The effective user ID is not the super-user, the effective user ID do match the
179 owner of the file, but the group ID of the file does not match the effective
180 group ID nor one of the supplementary group IDs.
182 The named file has its immutable or append-only flag set, see the
184 manual page for more information.
186 The named file resides on a read-only file system.
191 points outside the process's allocated address space.
193 An I/O error occurred while reading from or writing to the file system.
195 The effective user ID is not the super-user, the mode includes the sticky bit
197 and path does not refer to a directory.
202 system call will fail if:
205 The descriptor is not valid.
210 refers to a socket, not to a file.
212 The file resides on a read-only file system.
214 An I/O error occurred while reading from or writing to the file system.
226 system call is expected to conform to
228 except for the return of
239 system call appeared in
243 system call appeared in