What are permissions?

Every Unix file has a set of permissions associated with it that specify who is allowed to use that file and in what way.

There are three kinds of permissions:

A read permission means someone can see what is in the file.
A write permission means someone can change what is in the file, or even remove it.
An execute permission means someone can run (execute) a file, if that file contains a program.

Permissions are granted to three kinds of users:

The owner permissions specify what the owner of the file can do.
For a discussion of group permissions, see `Limiting file access to specific people'.
The world permissions specify what anyone can do.

Next: Finding a file's permissions
See also: Controlling access to your files; Changing file permissions
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John Shipman, john@nmt.edu