If you are developing a UNIX® application, then you can trace and debug the running application and extract the information you need from it. But what if you want to know what is going on inside a UNIX application and you don't have access to the source code?This tutorial looks at some systems that enable you to trace the execution of applications and work out what they are doing without having to make any modifications to the source code, and even without having to stop and restart the application.