1.\" $NetBSD: chmod.2,v 1.7 1995/02/27 12:32:06 cgd 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 fchmod 42.Nd change mode of file 43.Sh SYNOPSIS 44.Fd #include <sys/types.h> 45.Fd #include <sys/stat.h> 46.Ft int 47.Fn chmod "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 Chmod 64verifies that the process owner (user) either owns 65the file specified by 66.Fa path 67(or 68.Fa fd ) , 69or 70is the super-user. 71A mode is created from 72.Em or'd 73permission bit masks 74defined in 75.Aq Pa sys/stat.h : 76.Bd -literal -offset indent -compact 77#define S_IRWXU 0000700 /* RWX mask for owner */ 78#define S_IRUSR 0000400 /* R for owner */ 79#define S_IWUSR 0000200 /* W for owner */ 80#define S_IXUSR 0000100 /* X for owner */ 81 82#define S_IRWXG 0000070 /* RWX mask for group */ 83#define S_IRGRP 0000040 /* R for group */ 84#define S_IWGRP 0000020 /* W for group */ 85#define S_IXGRP 0000010 /* X for group */ 86 87#define S_IRWXO 0000007 /* RWX mask for other */ 88#define S_IROTH 0000004 /* R for other */ 89#define S_IWOTH 0000002 /* W for other */ 90#define S_IXOTH 0000001 /* X for other */ 91 92#define S_ISUID 0004000 /* set user id on execution */ 93#define S_ISGID 0002000 /* set group id on execution */ 94#define S_ISVTX 0001000 /* save swapped text even after use */ 95.Ed 96.Pp 97The 98.Dv ISVTX 99(the 100.Em sticky bit ) 101indicates to the system which executable files are shareable (the 102default) and the system maintains the program text of the files 103in the swap area. The sticky bit may only be set by the super user 104on shareable executable files. 105.Pp 106If mode 107.Dv ISVTX 108(the `sticky bit') is set on a directory, 109an unprivileged user may not delete or rename 110files of other users in that directory. The sticky bit may be 111set by any user on a directory which the user owns or has appropriate 112permissions. 113For more details of the properties of the sticky bit, see 114.Xr sticky 8 . 115.Pp 116Writing or changing the owner of a file 117turns off the set-user-id and set-group-id bits 118unless the user is the super-user. 119This makes the system somewhat more secure 120by protecting set-user-id (set-group-id) files 121from remaining set-user-id (set-group-id) if they are modified, 122at the expense of a degree of compatibility. 123.Sh RETURN VALUES 124Upon successful completion, a value of 0 is returned. 125Otherwise, a value of -1 is returned and 126.Va errno 127is set to indicate the error. 128.Sh ERRORS 129.Fn Chmod 130will fail and the file mode will be unchanged if: 131.Bl -tag -width Er 132.It Bq Er ENOTDIR 133A component of the path prefix is not a directory. 134.It Bq Er ENAMETOOLONG 135A component of a pathname exceeded 136.Dv {NAME_MAX} 137characters, or an entire path name exceeded 138.Dv {PATH_MAX} 139characters. 140.It Bq Er ENOENT 141The named file does not exist. 142.It Bq Er EACCES 143Search permission is denied for a component of the path prefix. 144.It Bq Er ELOOP 145Too many symbolic links were encountered in translating the pathname. 146.It Bq Er EPERM 147The effective user ID does not match the owner of the file and 148the effective user ID is not the super-user. 149.It Bq Er EROFS 150The named file resides on a read-only file system. 151.It Bq Er EFAULT 152.Fa Path 153points outside the process's allocated address space. 154.It Bq Er EIO 155An I/O error occurred while reading from or writing to the file system. 156.El 157.Pp 158.Fn Fchmod 159will fail if: 160.Bl -tag -width Er 161.It Bq Er EBADF 162The descriptor is not valid. 163.It Bq Er EINVAL 164.Fa Fd 165refers to a socket, not to a file. 166.It Bq Er EROFS 167The file resides on a read-only file system. 168.It Bq Er EIO 169An I/O error occurred while reading from or writing to the file system. 170.El 171.Sh SEE ALSO 172.Xr chmod 1 , 173.Xr open 2 , 174.Xr chown 2 , 175.Xr stat 2 , 176.Xr sticky 8 177.Sh STANDARDS 178The 179.Fn chmod 180function is expected to conform to 181.St -p1003.1-88 . 182.Sh HISTORY 183The 184.Fn fchmod 185function call 186appeared in 187.Bx 4.2 . 188