1.\" $OpenBSD: chmod.2,v 1.11 2003/06/02 20:18:39 millert Exp $ 2.\" $NetBSD: chmod.2,v 1.7 1995/02/27 12:32:06 cgd Exp $ 3.\" 4.\" Copyright (c) 1980, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd June 4, 1993 34.Dt CHMOD 2 35.Os 36.Sh NAME 37.Nm chmod , 38.Nm fchmod 39.Nd change mode of file 40.Sh SYNOPSIS 41.Fd #include <sys/types.h> 42.Fd #include <sys/stat.h> 43.Ft int 44.Fn chmod "const char *path" "mode_t mode" 45.Ft int 46.Fn fchmod "int fd" "mode_t mode" 47.Sh DESCRIPTION 48The function 49.Fn chmod 50sets the file permission bits of the file specified by the pathname 51.Fa path 52to 53.Fa mode . 54.Fn fchmod 55sets the permission bits of the specified file descriptor 56.Fa fd . 57.Fn chmod 58verifies that the process owner (user) either owns the file specified by 59.Fa path 60(or 61.Fa fd ) , 62or is the superuser. 63A mode is created from 64.Em or'd 65permission bit masks defined in 66.Aq Pa sys/stat.h : 67.Pp 68.Bd -literal -offset indent -compact 69#define S_IRWXU 0000700 /* RWX mask for owner */ 70#define S_IRUSR 0000400 /* R for owner */ 71#define S_IWUSR 0000200 /* W for owner */ 72#define S_IXUSR 0000100 /* X for owner */ 73 74#define S_IRWXG 0000070 /* RWX mask for group */ 75#define S_IRGRP 0000040 /* R for group */ 76#define S_IWGRP 0000020 /* W for group */ 77#define S_IXGRP 0000010 /* X for group */ 78 79#define S_IRWXO 0000007 /* RWX mask for other */ 80#define S_IROTH 0000004 /* R for other */ 81#define S_IWOTH 0000002 /* W for other */ 82#define S_IXOTH 0000001 /* X for other */ 83 84#define S_ISUID 0004000 /* set user id on execution */ 85#define S_ISGID 0002000 /* set group id on execution */ 86#define S_ISVTX 0001000 /* save swapped text even after use */ 87.Ed 88.Pp 89The 90.Dv ISVTX 91(the 92.Em sticky bit ) 93indicates to the system which executable files are shareable (the 94default) and the system maintains the program text of the files 95in the swap area. 96The sticky bit may only be set by the superuser on shareable executable files. 97.Pp 98If mode 99.Dv ISVTX 100(the 101.Dq sticky bit ) 102is set on a directory, an unprivileged user may not delete or rename 103files of other users in that directory. 104The sticky bit may be set by any user on a directory which the user owns 105or has appropriate permissions. 106For more details of the properties of the sticky bit, see 107.Xr sticky 8 . 108.Pp 109Writing or changing the owner of a file turns off the set-user-ID and 110set-group-ID bits unless the user is the superuser. 111This makes the system somewhat more secure by protecting 112set-user-ID (set-group-ID) files from remaining set-user-ID (set-group-ID) 113if they are modified, at the expense of a degree of compatibility. 114.Sh RETURN VALUES 115Upon successful completion, a value of 0 is returned. 116Otherwise, a value of \-1 is returned and 117.Va errno 118is set to indicate the error. 119.Sh ERRORS 120.Fn chmod 121will fail and the file mode will be unchanged if: 122.Bl -tag -width Er 123.It Bq Er ENOTDIR 124A component of the path prefix is not a directory. 125.It Bq Er ENAMETOOLONG 126A component of a pathname exceeded 127.Dv {NAME_MAX} 128characters, or an entire path name exceeded 129.Dv {PATH_MAX} 130characters. 131.It Bq Er ENOENT 132The named file does not exist. 133.It Bq Er EACCES 134Search permission is denied for a component of the path prefix. 135.It Bq Er EINVAL 136.Fa mode 137contains bits other than the file type and those described above. 138.It Bq Er ELOOP 139Too many symbolic links were encountered in translating the pathname. 140.It Bq Er EPERM 141The effective user ID does not match the owner of the file and 142the effective user ID is not the superuser. 143.It Bq Er EROFS 144The named file resides on a read-only file system. 145.It Bq Er EFAULT 146.Fa path 147points outside the process's allocated address space. 148.It Bq Er EIO 149An I/O error occurred while reading from or writing to the file system. 150.El 151.Pp 152.Fn fchmod 153will fail and the file mode will be unchanged if: 154.Bl -tag -width Er 155.It Bq Er EBADF 156The descriptor is not valid. 157.It Bq Er EINVAL 158.Fa fd 159refers to a socket, not to a file. 160.It Bq Er EINVAL 161.Fa mode 162contains bits other than the file type and those described above. 163.It Bq Er EROFS 164The file resides on a read-only file system. 165.It Bq Er EIO 166An I/O error occurred while reading from or writing to the file system. 167.El 168.Sh SEE ALSO 169.Xr chmod 1 , 170.Xr chown 2 , 171.Xr open 2 , 172.Xr stat 2 , 173.Xr sticky 8 174.Sh STANDARDS 175The 176.Fn chmod 177function is expected to conform to 178.St -p1003.1-88 . 179.Sh HISTORY 180The 181.Fn fchmod 182function call appeared in 183.Bx 4.2 . 184