1.\" $NetBSD: chmod.2,v 1.30 2005/01/06 16:30:52 ginsbach 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93 31.\" 32.Dd June 4, 1993 33.Dt CHMOD 2 34.Os 35.Sh NAME 36.Nm chmod , 37.Nm lchmod , 38.Nm fchmod 39.Nd change mode of file 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In sys/stat.h 44.Ft int 45.Fn chmod "const char *path" "mode_t mode" 46.Ft int 47.Fn lchmod "const char *path" "mode_t mode" 48.Ft int 49.Fn fchmod "int fd" "mode_t mode" 50.Sh DESCRIPTION 51The function 52.Fn chmod 53sets the file permission bits 54of the file 55specified by the pathname 56.Fa path 57to 58.Fa mode . 59.Fn fchmod 60sets the permission bits of the specified 61file descriptor 62.Fa fd . 63.Fn lchmod 64is like 65.Fn chmod 66except in the case where the named file is a symbolic link, 67in which case 68.Fn lchmod 69sets the permission bits of the link, 70while 71.Fn chmod 72sets the bits of the file the link references. 73.Fn chmod 74verifies that the process owner (user) either owns 75the file specified by 76.Fa path 77(or 78.Fa fd ) , 79or 80is the super-user. 81A mode is created from 82.Em or'd 83permission bit masks 84defined in 85.Aq Pa sys/stat.h : 86.Bd -literal -offset indent -compact 87#define S_IRWXU 0000700 /* RWX mask for owner */ 88#define S_IRUSR 0000400 /* R for owner */ 89#define S_IWUSR 0000200 /* W for owner */ 90#define S_IXUSR 0000100 /* X for owner */ 91 92#define S_IRWXG 0000070 /* RWX mask for group */ 93#define S_IRGRP 0000040 /* R for group */ 94#define S_IWGRP 0000020 /* W for group */ 95#define S_IXGRP 0000010 /* X for group */ 96 97#define S_IRWXO 0000007 /* RWX mask for other */ 98#define S_IROTH 0000004 /* R for other */ 99#define S_IWOTH 0000002 /* W for other */ 100#define S_IXOTH 0000001 /* X for other */ 101 102#define S_ISUID 0004000 /* set user id on execution */ 103#define S_ISGID 0002000 /* set group id on execution */ 104#define S_ISVTX 0001000 /* save swapped text even after use */ 105.Ed 106.Pp 107The 108.Dv ISVTX 109(the 110.Em sticky bit ) 111indicates to the system which executable files are shareable (the 112default) and the system maintains the program text of the files 113in the swap area. 114The sticky bit may only be set by the super user 115on shareable executable files. 116.Pp 117If mode 118.Dv ISVTX 119(the `sticky bit') is set on a directory, 120an unprivileged user may not delete or rename 121files of other users in that directory. 122The sticky bit may be set by any user on a directory which the user 123owns or has appropriate permissions. 124For more details of the properties of the sticky bit, see 125.Xr sticky 7 . 126.Pp 127Changing the owner of a file 128turns off the set-user-id and set-group-id bits; 129writing to a file 130turns off the set-user-id and set-group-id bits 131unless the user is the super-user. 132This makes the system somewhat more secure 133by protecting set-user-id (set-group-id) files 134from remaining set-user-id (set-group-id) if they are modified, 135at the expense of a degree of compatibility. 136.Sh RETURN VALUES 137Upon successful completion, a value of 0 is returned. 138Otherwise, a value of \-1 is returned and 139.Va errno 140is set to indicate the error. 141.Sh ERRORS 142.Fn chmod 143and 144.Fn lchmod 145will fail and the file mode will be unchanged if: 146.Bl -tag -width Er 147.It Bq Er ENOTDIR 148A component of the path prefix is not a directory. 149.It Bq Er ENAMETOOLONG 150A component of a pathname exceeded 151.Dv {NAME_MAX} 152characters, or an entire path name exceeded 153.Dv {PATH_MAX} 154characters. 155.It Bq Er ENOENT 156The named file does not exist. 157.It Bq Er EACCES 158Search permission is denied for a component of the path prefix. 159.It Bq Er ELOOP 160Too many symbolic links were encountered in translating the pathname. 161.It Bq Er EPERM 162The effective user ID does not match the owner of the file and 163the effective user ID is not the super-user. 164.It Bq Er EROFS 165The named file resides on a read-only file system. 166.It Bq Er EFAULT 167.Fa path 168points outside the process's allocated address space. 169.It Bq Er EIO 170An I/O error occurred while reading from or writing to the file system. 171.It Bq Er EFTYPE 172The effective user ID is not the super-user, the 173.Fa mode 174includes the sticky bit 175.Pq Dv S_ISVTX , 176and 177.Fa path 178does not refer to a directory. 179.El 180.Pp 181.Fn fchmod 182will fail if: 183.Bl -tag -width Er 184.It Bq Er EBADF 185The descriptor is not valid. 186.It Bq Er EINVAL 187.Fa fd 188refers to a socket, not to a file. 189.It Bq Er EPERM 190The effective user ID does not match the owner of the file and 191the effective user ID is not the super-user. 192.It Bq Er EROFS 193The file resides on a read-only file system. 194.It Bq Er EIO 195An I/O error occurred while reading from or writing to the file system. 196.It Bq Er EFTYPE 197The effective user ID is not the super-user, the 198.Fa mode 199includes the sticky bit 200.Pq Dv S_ISVTX , 201and 202.Fa fd 203does not refer to a directory. 204.El 205.Sh SEE ALSO 206.Xr chmod 1 , 207.Xr chflags 2 , 208.Xr chown 2 , 209.Xr open 2 , 210.Xr stat 2 , 211.Xr sticky 7 , 212.Xr symlink 7 213.Sh STANDARDS 214The 215.Fn chmod 216function conforms to 217.St -p1003.1-90 . 218.Sh HISTORY 219The 220.Fn fchmod 221function call 222appeared in 223.Bx 4.2 . 224The 225.Fn lchmod 226function call appeared in 227.Nx 1.3 . 228