1.\" $MirOS: src/lib/libc/sys/chmod.2,v 1.2 2007/05/19 21:47:41 tg Exp $ 2.\" $OpenBSD: chmod.2,v 1.13 2004/04/15 19:52:18 jmc Exp $ 3.\" $NetBSD: chmod.2,v 1.7 1995/02/27 12:32:06 cgd Exp $ 4.\" 5.\" Copyright (c) 1980, 1991, 1993 6.\" The Regents of the University of California. All rights reserved. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93 33.\" 34.Dd May 19, 2007 35.Dt CHMOD 2 36.Os 37.Sh NAME 38.Nm chmod , 39.Nm lchmod , 40.Nm fchmod 41.Nd change mode of a file or link 42.Sh SYNOPSIS 43.Fd #include <sys/types.h> 44.Fd #include <sys/stat.h> 45.Ft int 46.Fn chmod "const char *path" "mode_t mode" 47.Ft int 48.Fn lchmod "const char *path" "mode_t mode" 49.Ft int 50.Fn fchmod "int fd" "mode_t mode" 51.Sh DESCRIPTION 52The function 53.Fn chmod 54sets the file permission bits of the file specified by the pathname 55.Fa path 56to 57.Fa mode . 58.Fn lchmod 59operates similarly to 60.Fn chmod 61but does not follow symbolic links. 62It allows the permission bits of a symbolic link to be set. 63.Fn fchmod 64sets the permission bits of the specified file descriptor 65.Fa fd . 66.Fn chmod 67verifies that the process owner (user) either owns the file specified by 68.Fa path 69(or 70.Fa fd ) , 71or is the superuser. 72A mode is created from 73.Em or'd 74permission bit masks defined in 75.Aq Pa sys/stat.h : 76.Bd -literal -offset indent 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 97If mode 98.Dv ISVTX 99(the 100.Em sticky bit ) 101is set on a file, it is ignored. 102.Pp 103If mode 104.Dv ISVTX 105(the 106.Em sticky bit ) 107is set on a directory, an unprivileged user may not delete or rename 108files of other users in that directory. 109The sticky bit may be set by any user on a directory which the user owns 110or has appropriate permissions. 111For more details of the properties of the sticky bit, see 112.Xr sticky 8 . 113.Pp 114Writing or changing the owner of a file turns off the set-user-ID and 115set-group-ID bits unless the user is the superuser. 116This makes the system somewhat more secure by protecting 117set-user-ID (set-group-ID) files from remaining set-user-ID (set-group-ID) 118if they are modified, at the expense of a degree of compatibility. 119.Sh RETURN VALUES 120Upon successful completion, a value of 0 is returned. 121Otherwise, a value of \-1 is returned and 122.Va errno 123is set to indicate the error. 124.Sh ERRORS 125.Fn chmod 126or 127.Fn lchmod 128will fail and the file mode will be unchanged if: 129.Bl -tag -width Er 130.It Bq Er ENOTDIR 131A component of the path prefix is not a directory. 132.It Bq Er ENAMETOOLONG 133A component of a pathname exceeded 134.Dv {NAME_MAX} 135characters, or an entire path name exceeded 136.Dv {PATH_MAX} 137characters. 138.It Bq Er ENOENT 139The named file does not exist. 140.It Bq Er EACCES 141Search permission is denied for a component of the path prefix. 142.It Bq Er EINVAL 143.Fa mode 144contains bits other than the file type and those described above. 145.It Bq Er ELOOP 146Too many symbolic links were encountered in translating the pathname. 147.It Bq Er EPERM 148The effective user ID does not match the owner of the file and 149the effective user ID is not the superuser. 150.It Bq Er EROFS 151The named file resides on a read-only file system. 152.It Bq Er EFAULT 153.Fa path 154points outside the process's allocated address space. 155.It Bq Er EIO 156An I/O error occurred while reading from or writing to the file system. 157.El 158.Pp 159.Fn fchmod 160will fail and the file mode will be unchanged if: 161.Bl -tag -width Er 162.It Bq Er EBADF 163The descriptor is not valid. 164.It Bq Er EINVAL 165.Fa fd 166refers to a socket, not to a file. 167.It Bq Er EINVAL 168.Fa mode 169contains bits other than the file type and those described above. 170.It Bq Er EROFS 171The file resides on a read-only file system. 172.It Bq Er EIO 173An I/O error occurred while reading from or writing to the file system. 174.El 175.Sh SEE ALSO 176.Xr chmod 1 , 177.Xr chown 2 , 178.Xr open 2 , 179.Xr stat 2 , 180.Xr sticky 8 181.Sh STANDARDS 182The 183.Fn chmod 184function is expected to conform to 185.St -p1003.1-88 . 186.Sh HISTORY 187The 188.Fn fchmod 189function call appeared in 190.Bx 4.2 . 191The 192.Fn lchmod 193function call appeared in 194.Mx 10 . 195