Exploring Expect

The time Command

You may want to try different commands and algorithms to compare which is faster. You can use the timestamp command for this, but Tcl provides a built-in command called time which is more convenient.

The time command takes a command to execute and an optional iteration count. It returns a description of the time taken to execute each iteration. As an example, the following command times three iterations of "sleep 7“.

expect1.1> time {sleep 7} 3
7000327 microseconds per iteration

As you can see, each sleep took very close to 7 seconds which is what you would expect. The precise amount of time will vary from run to run depending on what else is executing at the same time, of course. So using a high iteration count can smooth out the difference and provide a more useful answer.

In some cases, it may be useful to run external performance monitors. For example, memory or network usage may be just as important to your application as CPU usage.