Imagine this scenario: while working on a project as a systems programmer (using C on Linux), there is a requirement that, from within the graphical user interface (GUI) frontend application, when the end user clicks a certain button, the application must display the content of a system-generated PDF document. We can assume a PDF reader software application is available to us. But, how exactly, will you run it from within your C code?

This chapter will teach you how to perform this important task. Here, we will learn some core Unix/Linux systems programming concepts: How the Unix exec model works, the predecessor/successor terminology, and how to use up to seven exec family APIs to make the whole thing actually work in code. Along the way, of course, code examples are used to clearly illustrate the concepts.

Briefly, the reader will learn about the following key areas:

• The meaning of the exec operation and its semantics
  • Testing the exec operation
  • Using the exec—the wrong and right ways to do so

• Error handling with the exec
• the seven exec family APIs and how to use them in code.