Fine; you can decipher the permissions for a file or directory, but what if you want to change them? Maybe you've decided that the pig_info file is a little too sensitive for just anybody to view, or that you should allow all users to execute the zippity program. The chmod (change mode) command can take care of that. The general form of the chmod command is

chmod <permission flags> <file or directory name(s)>

To tell chmod the new permissions for a file, you can use any combination of these permission flag characters:

Here are some examples:

chmod o-r pig_info Remove read access from all others.

chmod g+rw pig_info Grant read and write access to group.

chmod ugo+x zippity Grant execute access to everybody.

In effect, you're saying "change the mode for these people by adding/removing their access to read/write/execute the file named whatever." Just pick the proper combination of flags in each of the three columns, depending on what type of access you want for the file.

Note: If you give chmod a directory name instead of a file name, the permissions have slightly different meanings. For a directory, read access means that you can list the files with the ls command; write access allows you to create or delete files; and execute access gives you the ability to change to that directory with the cd command.

Transferring Ownership of a File Using Chown

If you are logged in as root, you can transfer ownership of a file or directory (if you move it into another user's directory) using the chown command.

To tell chown what to do, just give it the new owner and the file name, like this:

chown sigmund zippity

This will make sigmund the owner of zippity. Once you've transferred ownership, sigmund will be able to set the file's permissions (with chmod) if he wants to.

For more information on the chmod command, see the chmod manual.

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