NAME

chmod − change mode

SYNOPSIS

chmod mode files

DESCRIPTION

The permissions of the named files are changed according to mode, which may be absolute or symbolic. An absolute mode is an octal number constructed from the OR of the following modes:

4000 set user ID on execution

2000 set group ID on execution

1000 sticky bit, see chmod(2)

0400 read by owner

0200 write by owner

0100 execute (search in directory) by owner

0070 read, write, execute (search) by group

0007 read, write, execute (search) by others

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) 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 may 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) may change its mode. 

EXAMPLE

chmod 755 filename

changes the mode of "filename" to: read, write, execute (400+200+100) by owner; read, execute (40+10) for group; read, execute (4+1) for others.  An ls -l of filename shows [-rwxr-xr-x filename] that the requested mode is in effect. 

chmod = filename

will take away all permissions from filename, including yours.

chmod o-w file

denies write permission to others. 

chmod +x file

makes a file executable. 

SEE ALSO

ls(1), chmod(2). 

Version 2.1  —  January 02, 1985