Beginning Portable Shell Scripting: From Novice to Professional

CHAPTER 4Core Shell Features Explained

This chapter gives a more detailed explanation of the structure of shell programs and the interactions between some of the basic features introduced in Chapter 1. This chapter also introduces the basic grammatical structure of shell programs, then explores the interactions of the quoting, substitution, and globbing mechanisms.

There are a number of exceptions and special cases, which are explained throughout the chapter, but an overview makes it easier to follow what happens. The first thing the shell does is split input into words and special punctuation items, called tokens. After this, substitutions and expansions are performed, replacing variable references with the contents of variables, shell glob ...