1.\" $OpenBSD: chmod.2,v 1.10 2000/10/18 05:12:08 aaron 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. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93 36.\" 37.Dd June 4, 1993 38.Dt CHMOD 2 39.Os 40.Sh NAME 41.Nm chmod , 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 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 fchmod 59sets the permission bits of the specified file descriptor 60.Fa fd . 61.Fn chmod 62verifies that the process owner (user) either owns the file specified by 63.Fa path 64(or 65.Fa fd ) , 66or is the superuser. 67A mode is created from 68.Em or'd 69permission bit masks defined in 70.Aq Pa sys/stat.h : 71.Pp 72.Bd -literal -offset indent -compact 73#define S_IRWXU 0000700 /* RWX mask for owner */ 74#define S_IRUSR 0000400 /* R for owner */ 75#define S_IWUSR 0000200 /* W for owner */ 76#define S_IXUSR 0000100 /* X for owner */ 77 78#define S_IRWXG 0000070 /* RWX mask for group */ 79#define S_IRGRP 0000040 /* R for group */ 80#define S_IWGRP 0000020 /* W for group */ 81#define S_IXGRP 0000010 /* X for group */ 82 83#define S_IRWXO 0000007 /* RWX mask for other */ 84#define S_IROTH 0000004 /* R for other */ 85#define S_IWOTH 0000002 /* W for other */ 86#define S_IXOTH 0000001 /* X for other */ 87 88#define S_ISUID 0004000 /* set user id on execution */ 89#define S_ISGID 0002000 /* set group id on execution */ 90#define S_ISVTX 0001000 /* save swapped text even after use */ 91.Ed 92.Pp 93The 94.Dv ISVTX 95(the 96.Em sticky bit ) 97indicates to the system which executable files are shareable (the 98default) and the system maintains the program text of the files 99in the swap area. 100The sticky bit may only be set by the superuser on shareable executable files. 101.Pp 102If mode 103.Dv ISVTX 104(the 105.Dq sticky bit ) 106is set on a directory, an unprivileged user may not delete or rename 107files of other users in that directory. 108The sticky bit may be set by any user on a directory which the user owns 109or has appropriate permissions. 110For more details of the properties of the sticky bit, see 111.Xr sticky 8 . 112.Pp 113Writing or changing the owner of a file turns off the set-user-ID and 114set-group-ID bits unless the user is the superuser. 115This makes the system somewhat more secure by protecting 116set-user-ID (set-group-ID) files from remaining set-user-ID (set-group-ID) 117if they are modified, at the expense of a degree of compatibility. 118.Sh RETURN VALUES 119Upon successful completion, a value of 0 is returned. 120Otherwise, a value of \-1 is returned and 121.Va errno 122is set to indicate the error. 123.Sh ERRORS 124.Fn chmod 125will fail and the file mode will be unchanged if: 126.Bl -tag -width Er 127.It Bq Er ENOTDIR 128A component of the path prefix is not a directory. 129.It Bq Er ENAMETOOLONG 130A component of a pathname exceeded 131.Dv {NAME_MAX} 132characters, or an entire path name exceeded 133.Dv {PATH_MAX} 134characters. 135.It Bq Er ENOENT 136The named file does not exist. 137.It Bq Er EACCES 138Search permission is denied for a component of the path prefix. 139.It Bq Er EINVAL 140.Fa mode 141contains bits other than the file type and those described above. 142.It Bq Er ELOOP 143Too many symbolic links were encountered in translating the pathname. 144.It Bq Er EPERM 145The effective user ID does not match the owner of the file and 146the effective user ID is not the superuser. 147.It Bq Er EROFS 148The named file resides on a read-only file system. 149.It Bq Er EFAULT 150.Fa path 151points outside the process's allocated address space. 152.It Bq Er EIO 153An I/O error occurred while reading from or writing to the file system. 154.El 155.Pp 156.Fn fchmod 157will fail and the file mode will be unchanged if: 158.Bl -tag -width Er 159.It Bq Er EBADF 160The descriptor is not valid. 161.It Bq Er EINVAL 162.Fa fd 163refers to a socket, not to a file. 164.It Bq Er EINVAL 165.Fa mode 166contains bits other than the file type and those described above. 167.It Bq Er EROFS 168The file resides on a read-only file system. 169.It Bq Er EIO 170An I/O error occurred while reading from or writing to the file system. 171.El 172.Sh SEE ALSO 173.Xr chmod 1 , 174.Xr chown 2 , 175.Xr open 2 , 176.Xr stat 2 , 177.Xr sticky 8 178.Sh STANDARDS 179The 180.Fn chmod 181function is expected to conform to 182.St -p1003.1-88 . 183.Sh HISTORY 184The 185.Fn fchmod 186function call appeared in 187.Bx 4.2 . 188