Unix shell vi mode

Command Completion

Etc

Vi mode is a dinosaur, but still it's predominant mode used by in shell. I recommend to enable it in your profile if this was not done yet (unless you prefer Emacs mode). The simplest way to enable vi editing mode is to set the option explicitly with the set -o command:

$ set -o vi

Another way to enable vi command mode is to set global environment variable VISUAL in your .profile or environment file:

VISUAL=$(whence vi)
export VISUAL

Here whence is a built-in command that takes the name of another command as its argument and returns the command's full pathname on the standard output; the form $(command) returns the standard output generated by command as a string value. This trick make the assignment portable.

There are two interesting, but often overlooked features of vi mode:

The command history can be considered as an implicit editing buffer and the current command is just the last line of this buffer.
There is some (limited) ability to interact with current directory listing (command completion, which probably should be called filename completion).

Basic navigation

The most important vi-mode commands are as follow:

Command

Function

h Move left one character l Move right one character w Move right one word b Move left one word W Move to beginning of next non-blank word B Move to beginning of preceding non-blank word e Move to end of current word E Move to end of current non-blank word 0 Move to beginning of line ^ Move to first non-blank character in line $ Move to end of line

Up	Move back one command in the history list.
Down	Move forward one command in the history list.
Left	Move back one character.
Right	Move forward one character.
Esc f	Move forward one word.
Esc b	Move back one word.
Ctrl-A	Move to beginning of line.
Ctrl-E	Move to end of line.
Ctrl-D	Delete current character.
Backspace	Delete previous character.
Esc d	Delete current word.
Ctrl-U	Delete from beginning of line.
Esc k	Delete to end of line.
Ctrl-Y	Retrieve last item deleted.
Esc .	Insert last word of previous command.
Ctrl-L	Clear the screen, placing the current line at the top of the screen.
Tab	Attempt to complete the current word, interpreting it as a filename, username, variable name, hostname, or command as determined by the context.
Esc ?	List the possible completions.

One of the most useful editing keystrokes, Tab, can also be used when typing a command. If you type the first part of a filename and press Tab, the shell will attempt to locate files with names matching the characters you've typed. If exactly one such file exists, the shell fills out the partially typed name with the proper characters. You can then press Enter to execute the command or continue typing other options and arguments. This feature, called either filename completion or command completion, makes the shell much easier to use.

In addition to keystrokes for editing the command line, the shell interprets several keystrokes that control the operation of the currently executing program. For example, typing Ctrl-C generally cancels execution of a program. This keystroke command is handy, for example, when a program is taking too long to execute and you'd prefer to try something else.

Keystroke

Function

Ctrl-C	Sends an interrupt signal to the currently executing command, which generally responds by terminating itself.
Ctrl-D	Sends an end of file to the currently executing command. Use this keystroke to terminate console input.
Ctrl-Z	Suspends the currently executing program.

Several other special characters control the operation of the shell The # and ; characters are most often used in shell scripts, which you'll learn about later in this chapter. The & character is useful for running a command as a background process.

Character

Function

`#`	Marks the command as a comment, which the shell ignores.
`;`	Separates commands, letting you enter several commands on a single line.
`&`	Placed at the end of a command, causes the command to execute as a background process, so that a new shell prompt appears immediately after the command is entered.

Shell History

LUG@GT Using the Korn Shell

history [ -{num} | {num} {num} | {num} ]
That's limit list to num, display from num to num, and show commands starting from num.
r [ {num} | {string cmd starts with} ]
Recall a previous command by its history number or by typing in the first few characters of its name.

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Last modified: March 15, 2008