IN THIS CHAPTER
Expanding Null or Unset Variables
String Pattern Matching
Chapter 12 explained more about the shells, particularly the Bourne Again Shell. This chapter introduces additional commands, builtins, and concepts that carry shell programming to a point where it can be useful. The first programming constructs covered are control structures, or control flow constructs. These structures allow you to write scripts that can loop over command line arguments, make decisions based on the value of a variable, set up menus, and more. The Bourne Again Shell uses the same constructs found in such high-level programming languages as C.
This chapter ...