4.7.1. Word Completion

$ cd /usr/inc

Now press the Tab key. The shell will add lude to complete the name of the directory /usr/include. Now you can press the Return key, and the command will execute.

The criterion for specifying a filename is "minimal completion." Type just enough characters to distinguish a name from all the others in that directory. The shell can find the name and complete it — up to and including a slash, if the name is a directory.

You can use completion on commands too. For instance, if you type:

$ ema

and press the Tab key, the shell will add the cs to make emacs (unless some other command in your path begins with ema).

What if multiple files match what you've typed? If they all start with the same characters, the shell completes the word up to the point where names differ. Beyond that, most shells do nothing. bash has a neat enhancement: if you press the Tab key twice, it displays all the possible completions. For instance, if you enter:

$ cd /usr/l

and press the Tab key twice, bash prints something like:

lib         local

4.7.2. Moving Around Among Commands

As an example, suppose you tried to execute:

$ mroe .bashrc
bash: mroe: command not found

Of course, you typed mroe instead of more. To correct the command, call it back by pressing the up arrow. Then press the left arrow until the cursor lies over the o in mroe. You could use the Backspace key to remove the o and r and retype them correctly. But here's an even neater shortcut: just press Ctrl-T. It will reverse o and r, and you can then press the Return key to execute the command.

Many other key combinations exist for command-line editing. But the basics shown here will help you quite a bit. If you learn the Emacs editor, you will find that most keys work the same way in the shell. And if you're a vi fan, you can set up your shell so that it uses vi key bindings instead of Emacs bindings. To do this in bash, ksh, or zsh, enter the command:

$ export VISUAL=vi

In tcsh enter:

$ setenv VISUAL vi