Chapter 9. Working with the POSIX Shell and Job Control | HP Certified: HP-UX System Administration

Chapter Syllabus

9.1 POSIX Shell Capabilities

9.2 File Name Completion

9.3 History and Reentering Commands

9.4 Command Line Editing

9.5 Substitution

9.6 Setting Terminal Parameters

9.7 Job Control

The shell is an interactive program that gets user input, interprets it, and then takes necessary action accordingly . It acts like a command interpreter for the user. As soon as a command is received from a user, the shell looks for a matching intrinsic command and executes it. If it does not find an intrinsic command, it searches for a disk file corresponding to the command and executes it. During this process it substitutes any variables and other commands listed in the command line. It also handles I/O redirection and can execute batch files containing other UNIX commands and control structures.

You are already familiar with many of the shell features, such as environment variables, intrinsic and extrinsic commands, shell history, and shell configuration files. In this chapter, more features of the POSIX shell are presented. These include file name completion, setting terminal options, and job control. There is more information in this chapter on some of the features you are already familiar with. These include shell history, command line editing, and substitution. We will start with a comparison of the capabilities of different UNIX shells and see what the subshells are. Then there is a brief introduction to the ulimit command that is used for limiting system resources. File name completion and shell history will be discussed next . Then you will find some more information on command line editing and substitution. In the substitution process, you will see how command substitution, variable substitution, and tilde substitution work. While working on different terminals, you may need to set some of the terminals' parameters, and you will learn the stty command that is used for this purpose. In the last part of the chapter, job control features of the POSIX shell are discussed.

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