8.17. Summary

A thorough understanding of the UNIX System's process control is essential for advanced programming. There are only a few functions to master: fork, the exec family, _exit, wait, and waitpid. These primitives are used in many applications. The fork function also gave us an opportunity to look at race conditions.

Our examination of the system function and process accounting gave us another look at all these process control functions. We also looked at another variation of the exec functions: interpreter files and how they operate. An understanding of the various user IDs and group IDs that are providedreal, effective, and savedis critical to writing safe set-user-ID programs.

Given an understanding of a single process and its children, in the next chapter we examine the relationship of a process to other processessessions and job control. We then complete our discussion of processes in Chapter 10 when we describe signals.