Section 7.12. Summary

7.12. Summary

Understanding the environment of a C program in a UNIX system's environment is a prerequisite to understanding the process control features of the UNIX System. In this chapter, we've looked at how a process is started, how it can terminate, and how it's passed an argument list and an environment. Although both are uninterpreted by the kernel, it is the kernel that passes both from the caller of exec to the new process.

We've also examined the typical memory layout of a C program and how a process can dynamically allocate and free memory. It is worthwhile to look in detail at the functions available for manipulating the environment, since they involve memory allocation. The functions setjmp and longjmp were presented, providing a way to perform nonlocal branching within a process. We finished the chapter by describing the resource limits that various implementations provide.