Command Line Editor

OpenBoot specifies a required command line editor (similar to EMACS, a common text editor), some optional extensions and an optional history mechanism for the User Interface. Use these powerful tools to re-execute previous commands without retyping them, to edit the current command line to fix typing errors, or to recall and change previous commands.

Table 4-16 lists the required line-editing commands available at the ok prompt.

Table 4-16 Required Command Line Editor Keystroke Commands

Keystroke	Description
Delete	Erases previous character.
Backspace	Erases previous character.
Control-U	Erases the line.
Return (Enter)	Finishes editing of the line and submits the entire visible line to the interpreter regardless of the current cursor position.

The OpenBoot standard also describes three groups of extensions of these capabilities. Table 4-17 lists the command line editing extension group.

Table 4-17 Optional Command Line Editor Keystroke Commands

Keystroke	Description
Control-B	Moves backward one character.
Escape B	Moves backward one word.
Control-F	Moves forward one character.
Escape F	Moves forward one word.
Control-A	Moves backward to beginning of line.
Control-E	Moves forward to end of line.
Delete	Erases previous character.
Backspace	Erases previous character.
Control-H	Erases previous character.
Escape H	Erases from beginning of word to just before the cursor, storing erased characters in a save buffer.
Control-W	Erases from beginning of word to just before the cursor, storing erased characters in a save buffer.
Control-D	Erases next character.
Escape D	Erases from cursor to end of the word, storing erased characters in a save buffer.
Control-K	Erases from cursor to end of line, storing erased characters in a save buffer.
Control-U	Erases entire line, storing erased characters in a save buffer.
Control-R	Retypes the line.
Control-Q	Quotes next character (allows you to insert control characters).
Control-Y	Inserts the contents of the save buffer before the cursor.

The command line history extension enables previously-typed commands to be saved in an EMACS-like command history ring that contains at least 8 entries. Commands may be recalled by moving either forward or backward around the ring. Once recalled, a command may be edited and/or re-submitted (by typing the Return key). The command line history extension keys are:

Table 4-18 Optional Command Line History Keystroke Commands

Keystroke	Description
Control-P	Selects and displays the previous command in the command history ring.
Control-N	Selects and displays the next command in the command history ring.
Control-L	Displays the entire command history ring.

The command completion extension enables the system to complete long Forth word names by searching the dictionary for one or more matches based upon the already-typed portion of a word. After you type in a portion of a word followed by the command completion keystroke, Control-Space, the system responds as follows:

• If the system finds exactly one matching word, the remainder of the word is automatically displayed.

• If the system finds several possible matches, it displays all characters common to all possibilities.

• If the system cannot find a match for the already-typed characters, it deletes characters from the right until there is at least one match for the remaining characters.

• The system beeps if it cannot determine an unambiguous match.

The command completion extension keys are:

Table 4-19 Optional Command Completion Keystroke Commands

Keystroke	Description
Control-Space	Complete the name of the current word.
Control-?	Display all possible matches for the current word.
Control-/	Display all possible matches for the current word.