File Permissions and Privacy

File permissions are rules attached to a file or folder that control what each user may do with it. A permission can let you read an item but not change it, let you edit or delete it, or block you from it completely.

Permissions are set on the file, but they are checked against the user who is logged in. Before carrying out any action, the operating system checks that user's permissions. This is why you might see that a file exists and still be stopped from opening, changing or deleting it.

What each permission allows

• Read — open and view the item. A read-only file opens normally, but any attempt to save changes over it is refused.
• Edit — change the contents and save them.
• Delete — remove the item from its folder.
• No access — the item is refused, or hidden from you altogether.

Permissions keep users' files private

This is where file management and user management meet. User management gives each person an account; file permissions then use that account to decide whose work area can be opened. Setting your own folder so that other standard users have no access keeps your work private on a machine that several people use.

For example, on a youth theatre group's laptop the treasurer keeps a folder of ticket receipts that only the treasurer's account can read, edit or delete. The committee's budget summary can be read by every committee member, but only the treasurer may change it. The shared script folder can be read by everyone and edited by committee members.

File permissions are not access rights

Access rights decide what you may do on the whole computer, such as installing software. File permissions decide what you may do with one particular file or folder, so they belong to file management.