User Interface

A program that uses this library provides a simple emacs-like editing interface to its users. A line may be edited before it is sent to the calling program by typing either control characters or escape sequences. A control character, shown as a caret followed by a letter, is typed by holding down the control key while the letter is typed. For example, ^A is a control-A. An escape sequence is entered by typing the escape key followed by one or more characters. The escape key is abbreviated as ESC. Note that unlike control keys, case matters in escape sequences; ESC F is not the same as ESC f.

An editing command may be typed anywhere on the line, not just at the beginning. In addition, a return may also be typed anywhere on the line, not just at the end.

Most editing commands may be given a repeat count, n, where n is a number. To enter a repeat count, type the escape key, the number, and then the command to execute. For example, ESC 4 ^f moves forward four characters. If a command may be given a repeat count then the text [n] is given at the end of its description.

The following control characters are accepted:

^A

Move to the beginning of the line

^B

Move left (backwards) [n]

^D

Delete character [n]

^E

Move to end of line

^F

Move right (forwards) [n]

^G

Ring the bell

^H

Delete character before cursor (backspace key) [n]

^I

Complete filename (tab key); see below

^J

Done with line (return key)

^K

Kill to end of line (or column [n])

^L

Redisplay line

^M

Done with line (alternate return key)

^N

Get next line from history [n]

^P

Get previous line from history [n]

^R

Search backward (forward if [n]) through history for text; prefixing the string with a caret (^) forces it to match only at the beginning of a history line

^T

Transpose characters

^V

Insert next character, even if it is an edit command

^W

Wipe to the mark

^X^X

Exchange current location and mark

^Y

Yank back last killed text

^[

Start an escape sequence (escape key)

^]c

Move forward to next character c

^?

Delete character before cursor (delete key) [n]

The following escape sequences are provided:

ESC ^H

Delete previous word (backspace key) [n]

ESC DEL

Delete previous word (delete key) [n]

ESC SP

Set the mark (space key); see ^X^X and ^Y above

ESC .

Get the last (or [n]'th) word from previous line

ESC ?

Show possible completions; see below

ESC <

Move to start of history

ESC >

Move to end of history

ESC b

Move backward a word [n]

ESC d

Delete word under cursor [n]

ESC f

Move forward a word [n]

ESC l

Make word lowercase [n]

ESC m

Toggle if 8bit chars display normally or with an M- prefix

ESC u

Make word uppercase [n]

ESC y

Yank back last killed text

ESC v

Show library version

ESC w

Make area up to mark yankable

ESC nn

Set repeat count to the number nn

ESC C

Read from environment variable $C, where C is an uppercase letter

The editline library has a small macro facility. If you type the escape key followed by an uppercase letter, C, then the contents of the environment variable $C are read in as if you had typed them at the keyboard. For example, if the variable $L contains the following:

Then typing ESC L will move to the beginning of the line, kill the entire line, enter the echo command needed to clear the terminal (if your terminal is like a VT-100), and send the line back to the shell.

The editline library also does filename completion. Suppose the root directory has the following files in it:

If you type rm /v and then the tab key, editline will then finish off as much of the name as possible by adding munix. Because the name is not unique, it will then beep. If you type the escape key and a question mark, it will display the two choices. If you then type a period and a tab, the library will finish off the filename for you:

The tab key is shown by [TAB] and the automatically-entered text is shown in italics, or underline.

Example

The following brief example lets you enter a line and edit it, then displays it.

#include <stdio.h>
#include <stdlib.h>
#include <editline.h>

int main(void)
{
	char *p;

	while ((p = readline("CLI> "))) {
	        puts(p);
	        free(p);
	}

	return 0;
}