3.9.4 Changing permissions

        The command chmod is used to set the permissions on a file. Only the owner of a file may change the permissions on that file. The syntax of chmod is:

chmod {a,u,g,o}{+,-}{r,w,x}

Briefly, you supply one or more of all, user, group, or other. Then you specify whether you are adding rights (+) or taking them away (-). Finally, you specify one or more of read, write, and execute. Some examples of legal commands are:

chmod a+r stuff

Gives all users read access to the file.

chmod +r stuff

Same as above---if none of a, u, g, or o is specified, a is assumed.

chmod og-x stuff

Remove execute permission from users other than the owner.

chmod u+rwx stuff

Allow the owner of the file to read, write, and execute the file.

chmod o-rwx stuff

Remove read, write, and execute permission from users other than the owner and users in the file's group.