1.\" $NetBSD: chmod.2,v 1.15 1997/10/11 03:34:00 enami Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt CHMOD 2 38.Os BSD 4 39.Sh NAME 40.Nm chmod , 41.Nm lchmod , 42.Nm fchmod 43.Nd change mode of file 44.Sh SYNOPSIS 45.Fd #include <sys/types.h> 46.Fd #include <sys/stat.h> 47.Ft int 48.Fn chmod "const char *path" "mode_t mode" 49.Ft int 50.Fn lchmod "const char *path" "mode_t mode" 51.Ft int 52.Fn fchmod "int fd" "mode_t mode" 53.Sh DESCRIPTION 54The function 55.Fn chmod 56sets the file permission bits 57of the file 58specified by the pathname 59.Fa path 60to 61.Fa mode . 62.Fn fchmod 63sets the permission bits of the specified 64file descriptor 65.Fa fd . 66.Fn lchmod 67is like 68.Fn chmod 69except in the case where the named file is a symbolic link, 70in which case 71.Fn lchmod 72sets the permission bits of the link, 73while 74.Fn chmod 75sets the bits of the file the link references. 76.Fn chmod 77verifies that the process owner (user) either owns 78the file specified by 79.Fa path 80(or 81.Fa fd ) , 82or 83is the super-user. 84A mode is created from 85.Em or'd 86permission bit masks 87defined in 88.Aq Pa sys/stat.h : 89.Bd -literal -offset indent -compact 90#define S_IRWXU 0000700 /* RWX mask for owner */ 91#define S_IRUSR 0000400 /* R for owner */ 92#define S_IWUSR 0000200 /* W for owner */ 93#define S_IXUSR 0000100 /* X for owner */ 94 95#define S_IRWXG 0000070 /* RWX mask for group */ 96#define S_IRGRP 0000040 /* R for group */ 97#define S_IWGRP 0000020 /* W for group */ 98#define S_IXGRP 0000010 /* X for group */ 99 100#define S_IRWXO 0000007 /* RWX mask for other */ 101#define S_IROTH 0000004 /* R for other */ 102#define S_IWOTH 0000002 /* W for other */ 103#define S_IXOTH 0000001 /* X for other */ 104 105#define S_ISUID 0004000 /* set user id on execution */ 106#define S_ISGID 0002000 /* set group id on execution */ 107#define S_ISVTX 0001000 /* save swapped text even after use */ 108.Ed 109.Pp 110The 111.Dv ISVTX 112(the 113.Em sticky bit ) 114indicates to the system which executable files are shareable (the 115default) and the system maintains the program text of the files 116in the swap area. The sticky bit may only be set by the super user 117on shareable executable files. 118.Pp 119If mode 120.Dv ISVTX 121(the `sticky bit') is set on a directory, 122an unprivileged user may not delete or rename 123files of other users in that directory. The sticky bit may be 124set by any user on a directory which the user owns or has appropriate 125permissions. 126For more details of the properties of the sticky bit, see 127.Xr sticky 8 . 128.Pp 129Changing the owner of a file 130turns off the set-user-id and set-group-id bits; 131writing to a file 132turns off the set-user-id and set-group-id bits 133unless the user is the super-user. 134This makes the system somewhat more secure 135by protecting set-user-id (set-group-id) files 136from remaining set-user-id (set-group-id) if they are modified, 137at the expense of a degree of compatibility. 138.Sh RETURN VALUES 139Upon successful completion, a value of 0 is returned. 140Otherwise, a value of -1 is returned and 141.Va errno 142is set to indicate the error. 143.Sh ERRORS 144.Fn chmod 145and 146.Fn lchmod 147will fail and the file mode will be unchanged if: 148.Bl -tag -width Er 149.It Bq Er ENOTDIR 150A component of the path prefix is not a directory. 151.It Bq Er ENAMETOOLONG 152A component of a pathname exceeded 153.Dv {NAME_MAX} 154characters, or an entire path name exceeded 155.Dv {PATH_MAX} 156characters. 157.It Bq Er ENOENT 158The named file does not exist. 159.It Bq Er EACCES 160Search permission is denied for a component of the path prefix. 161.It Bq Er ELOOP 162Too many symbolic links were encountered in translating the pathname. 163.It Bq Er EPERM 164The effective user ID does not match the owner of the file and 165the effective user ID is not the super-user. 166.It Bq Er EROFS 167The named file resides on a read-only file system. 168.It Bq Er EFAULT 169.Fa path 170points outside the process's allocated address space. 171.It Bq Er EIO 172An I/O error occurred while reading from or writing to the file system. 173.It Bq Er EFTYPE 174The effective user ID is not the super-user, the 175.Fa mode 176includes the sticky bit 177.Pq Dv S_ISVTX , 178and 179.Fa path 180does not refer to a directory. 181.El 182.Pp 183.Fn fchmod 184will fail if: 185.Bl -tag -width Er 186.It Bq Er EBADF 187The descriptor is not valid. 188.It Bq Er EINVAL 189.Fa fd 190refers to a socket, not to a file. 191.It Bq Er EROFS 192The file resides on a read-only file system. 193.It Bq Er EIO 194An I/O error occurred while reading from or writing to the file system. 195.It Bq Er EFTYPE 196The effective user ID is not the super-user, the 197.Fa mode 198includes the sticky bit 199.Pq Dv S_ISVTX , 200and 201.Fa fd 202does not refer to a directory. 203.El 204.Sh SEE ALSO 205.Xr chmod 1 , 206.Xr chown 2 , 207.Xr open 2 , 208.Xr stat 2 , 209.Xr sticky 8 210.Sh STANDARDS 211The 212.Fn chmod 213function conforms to 214.St -p1003.1-90 . 215.Sh HISTORY 216The 217.Fn fchmod 218function call 219appeared in 220.Bx 4.2 . 221The 222.Fn lchmod 223function call appeared in 224.Nx 1.3 . 225