Exploring Expect

Dangerous, Unfriendly, Or Otherwise Unlikable User Interfaces

The interact command is just a shorthand for the simplest and most common types of filtering that can be done in interactions. It is possible to build arbitrarily sophisticated mechanisms using the tools in Expect.

For example, commands can be filtered out of interfaces to prevent users from entering commands that you would prefer they not enter. Programs can also be wrapped even more tightly. The adb program, for instance, can crash a UNIX system with a slip of the finger or, more likely, inexperience. You can prevent this from happening by securely wrapping the adb program in a script. Not only does this increase the safety of your system, but your system administrators no longer all have to be masters of its intricacies.

The UNIX dump program is another program with an unlikable interface. For example, dump often guesses incorrectly about the length of a tape and will prompt for a new tape even if one is not needed. An Expect script can be used to respond to dump so that it can continue automatically. A script can answer just this question or any question from dump.

Expect can, in general, be applied to interfaces that you simply do not like for whatever reason. For example, you might like to automate sequences of your favorite game, perhaps because you have long since mastered some of it and would like to practice the end game but without laboriously replaying the beginning each time.

It is possible to customize exactly ...