16.4) Group Permissions

Digits 5-7 are the permissions you can set to control how people in your group can interact with your files. Typically the permissions will be ‘r--‘ in columns 5 to 7 for files. This means that people in your group could read those files but not modify them or run them. If your files are very private then you can change the permission of people in your group to not be able to even view your files by typing:

chmod g-r filename

chmod is the command to change permissions, ‘g’ indicates you want to change the group permissions and ‘-r’ means take away reading permission on the file called ‘filename’. If on the other hand you want to add back reading permission and you want to allow your group to modify the file and save changes (write to disk) then type:

chmod g+rw filename