NAME

chmod − change file mode

SYNOPSIS

chmod [ −A ] mode file ... 

DESCRIPTION

Options

−A Preserve any optional access control list (ACL) entries associated with the file.  (By default, in conformance with the IEEE Standard POSIX 1003.1-1988, optional ACL entries are deleted.)  For information about access control lists, see acl(5).

The permissions of any named file are changed according to mode, which can be absolute or symbolic. An absolute mode is an octal number constructed from the logical OR of the following mode bits:

Miscellaneous mode bits:

  ______________ 4000  set user ID on execution (file)
|                       or hide directory (see cdf(4))
|      ________ 2000  set group ID on execution
|     |      __ 1000  sticky bit; see chmod(2)
|     |     |
s     s     t

Permission mode bits:

  __________________ 0400  read by owner
|  ________________ 0200  write by owner
| |  ______________ 0100  execute (search in directory) by owner
| | |  ____________ 0040  read by group
| | | |  __________ 0020  write by group
| | | | |  ________ 0010  execute/search by group
| | | | | |  ______ 0004  read by others
| | | | | | |  ____ 0002  write by others
| | | | | | | |  __ 0001  execute/search by others
| | | | | | | | |
r w x r w x r w x

A symbolic mode has the form:

[ who ] op permission [ op permission ]

The who part is a combination of the letters u (for user’s permissions), g (group) and o (other).  The letter a stands for ugo, the default if who is omitted. 

Op can be + to add permission to the file’s mode, − to take away permission, or = to assign permission absolutely (all other bits will be reset). 

Permission is any combination of the letters r (read), w (write), x (execute), s (set owner or group ID), H (hide directory), and t (save text or sticky); u, g or o indicate that permission is to be taken from the current mode.  Omitting permission is only useful with = to take away all permissions. 

Multiple symbolic modes separated by commas can be given.  Operations are performed in the order specified.  The letter s is only useful with u or g and t only works with u. 

Only the owner of a file (or the super-user) can change its mode.  Only the super-user can set the sticky bit.  In order to set the group ID, the group of the file must correspond to your current group ID. 

When using chmod on a symbolic link, the mode of the file referred to by the link is changed. 

RETURN VALUE

Exit values are:

 0 Successful completion. 

>0 Error condition occured. 

EXAMPLES

Deny write permission to others:

chmod o−w file

Make a file executable:

chmod +x file

Assign read and execute permission to everybody, and sets the set-user-ID bit:

chmod 4555 file

Assign read and write permission to the file owner, and read permission to everybody else:

chmod 644 file

DEPENDENCIES

RFA and NFS
The −A option is not supported for networked files. 

HP Clustered Environment
The absolute mode of 4000 also serves to hide a directory.  For symbolic mode, the permission letter H is used to hide a directory (see cdf(4)). 

AUTHOR

Chmod was developed by AT&T and HP. 

SEE ALSO

chacl(1), ls(1), chmod(2), cdf(4), acl(5). 

EXTERNAL INFLUENCES

International Code Set Support

Single- and multi-byte character code sets are supported. 

STANDARDS CONFORMANCE

chmod: SVID2, XPG2, XPG3

Hewlett-Packard Company  —  HP-UX Release 7.0: Sept 1989