In this chapter we have seen that bash provides command-line editing with two modes: vi and emacs.
You may be wondering why these two editors were chosen. The primary reason is because vi and emacs are the most widely used editors for UNIX. People who have used either editor will find familiar editing facilities.
If you are not familiar with either of these editors, you should seriously consider adopting emacs-mode keyboard habits. Because it is based on control keys and doesn't require you to think in terms of a "command mode" and
"insert mode," you will find emacs-mode easier to assimilate. Although the full emacs is an extremely powerful editor, its command structure lends itself very well to small subsetting: there are several "mini-emacs"
editors floating around for UNIX, MS-DOS, and other systems.
The same cannot be said for vi, because its command structure is really meant for use in a full-screen editor.vi is quite powerful too, in its way, but its power becomes evident only when it is used for purposes similar to that for which it was designed: editing source code in C and LISP. As mentioned earlier, a vi user has the power to move mountains in few keystrokes—but at the cost of being unable to do anything meaningful in very few keystrokes. Unfortunately, the latter is most desired in a
command interpreter, especially nowadays when users are spending more time within applications and less time working with the shell. In short, if you don't already know vi, you will probably find its commands obscure and confusing.
Both bash editing modes have quite a few commands;
you will undoubtedly develop keyboard habits that include just a few of them. If you use emacs-mode and you aren't familiar with the full emacs, here is a subset that is easy to learn yet enables you to do just about anything:
• For cursor motion around a command line, stick to CTRL-A and CTRL-E for beginning and end of line, and CTRL-F and CTRL-B for moving around.
• Delete using DEL (or whatever your "erase" key is) and CTRL-D; as with CTRL-F and CTRL-B, hold down to repeat if necessary. Use CTRL-K to erase the entire line.
• Use CTRL-P and CTRL-N (or the up and down arrow keys) to move through the command history.
• Use CTRL-R to search for a command you need to run again.
• Use TAB for filename completion.
After a few hours spent learning these keystrokes, you will wonder how you ever got along without command-line editing.
Chapter 3. Customizing Your Environment
An environment is a collection of concepts that express the things a computer system or other set of tools does in terms designed to be understandable and coherent, and a look and feel that is comfortable. For example, your desk at work is an environment. Concepts involved in desk work usually include memos, phone calls, letters, forms, etc. The tools on or in your desk that you use to deal with these things include paper, staples, envelopes, pens, a telephone, a calculator, etc. Every one of these has a set of characteristics that express how you use it; such characteristics range from location on your desk or in a drawer (for simple tools) to more sophisticated things like which numbers the memory buttons on your phone are set to. Taken together, these characteristics make up your desk's look and feel.
You customize the look and feel of your desk environment by putting pens where you can most easily reach them, programming your phone buttons, etc. In general, the more customization you have done, the more tailored to your personal needs—and therefore the more productive—your environment is.
Similarly, UNIX shells present you with such concepts as
UNIX itself gives you tools to work with these, such as file manipulation commands, text editors, and print queues. Your UNIX environment's look and feel is determined by your keyboard and display, of course, but also by how you set up your directories, where you put each kind of file, and what names you give to files, directories, and commands. There are also more sophisticated ways of customizing your shell environment.
This chapter will look at the four most important features thatbashprovides for customizing your environment.
Special files
The files .bash_profile, .bash_logout, and .bashrc that are read bybashwhen you log in and out or start a new shell.
Aliases
Synonyms for commands or command strings that you can define for convenience.
Options
Controls for various aspects of your environment that you can turn on and off.
Variables
Changeable values that are referred to by a name.
The shell and other programs can modify their
behavior according to the values stored in the variables.
Although these features are not the only ones available, they form the basis for doing more advanced customization. They are also the features that are common to the various shells available on UNIX. Later chapters will cover more advanced shell features, such as the ability to program the shell.