Exploring Expect

Chapter 4. Glob Patterns And Other Basics

In the last chapter, I showed some simple patterns that allow you to avoid having to specify exactly what you want to wait for. In this chapter, I will describe how to use patterns that you are already probably familiar with from the shell—glob patterns. I will also describe what happens when patterns do not match. I will go over some other basic situations such as how to handle timeouts. Finally I will describe what to do at theends of scripts and processes.

The * Wildcard

Suppose you want to match all of the input and the only thing you know about it is that hi occurs within it. You are not sure if there is more to it, or even if another hi might appear. You just want to get it all. To do this, use the asterisk (*). The asterisk is a wildcard that matches any number of characters. You can write:

expect "hi*"
send "$expect_out(0,string) $expect_out(buffer)"

If the input buffer contained "philosophic\n“, expect would match the entire buffer. Here is the output from the previous commands:

hilosophic
 philosophic

The pattern hi matched the literal hi while the * matched the string "losophic\n“. The first p was not matched by anything in the pattern so it shows up in expect_out(buffer) but not in expect_out(0,string).

Earlier I said that * matches any number of characters. More precisely, it tries to match the longest string possible while still allowing the pattern itself to match. With the input buffer of "philosophic\n“, compare the effects ...