This chapter describes the powerful BASH shell, providing a much more detailed explanation than that provided in Chapter 4. The chapter also briefly explains shell variables, shell scripts, and shell aliases, preparing you for an in-depth, continuing study of Linux.
You met the Linux command interpreter, or shell, early in this book. Like an MS-DOS Prompt window, the shell lets you issue commands that it interprets, or executes. By means of the shell, you use and control your system.
The MS-DOS shell has been fairly consistent over time; for example, the differences between MS-DOS v3 and MS-DOS v7 are few. The Unix shell, however, has experienced significantly more evolutionary development than MS-DOS. Today, you find both versions and variants of the Unix shell. The Unix shell variants have much in common, but each has a different authorship and history, and each reflects a different view of how users should interact with Unix.
Linux includes the most popular Unix shells, as shown in Table 13.1. The most popular Linux shell is the BASH shell (the “Bourne Again SHell”), based on the original Unix Bourne shell. The BASH shell is largely compliant with the POSIX standard, which specifies the syntax and operation of a standard Unix shell and which has been widely implemented. Because of the popularity of the POSIX standard and the obvious advantage of working with a shell that’s consistent across ...