Advanced UNIX Programming

Permissions

It is generally assumed in this book that the reader is already familiar with the UNIX access conventions that are applied. At the risk of stating the obvious, it is often useful at this stage to restate the precise way that permissions affect certain categories of file system objects. This is important because there are some minor semantic differences that depend on the file system object type.

Access of Regular Files

This is perhaps the simplest case to consider. Files can be controlled by

• Read access

• Write access

• Execute access

These are relatively simple concepts. However, a couple of interesting combinations exist:

• A file that has read and execute access

• A file that has execute-only access

The first case is necessary for shell ...