ed-debby

A personal learning project rewriting the venerable ed line editor in Rust.

Why ed?

• CLI editors are cool, and are useful for things like non-interactive text twiddling, big search/replace operations, and zero-distraction editing.
• Most of the behavior fits on one man page.
• Limited programming scope to focus on doing it right.
• Getting practice with parsing and domain-specific language implementation.

Why is the project called ed-debby?

First commits were made during hurricane Debby, 2024.

Differences so Far

It probably won't be possible to get full compatibility, particularly in the area of regular expression processing. If compatibility is a concern, please use the default ed. Here are some differences so far:

• Gnu ed uses a linked list for the buffer structure. Rust sources strongly recommend Rust's dynamic vector or other data structures instead. For now that seems like a safe bet.
• Command history, editing, and other quality-of-life features provided by rustyline.

Implemented and Planned Features

Ranges

• . - Represents the current line in the buffer.
• $ - Refers to the last line in the buffer.
• n - Targets the nth line in the buffer, where n is a number in the range [0,$].
• TODO - or ^ - Moves to the previous line. This is equivalent to -1 and may be repeated with cumulative effect.
• TODO -n or ^n - Moves to the nth previous line, where n is a non-negative number.
• TODO + - Moves to the next line. This is equivalent to +1 and may be repeated with cumulative effect.
• TODO +n - Moves to the nth next line, where n is a non-negative number.
• , or % - Selects the first through last lines in the buffer. This is equivalent to the address range 1,$.
• ; - Selects from the current through last lines in the buffer. This is equivalent to the address range .,$.
• TODO /re/ - Searches for the next line containing the regular expression re. The search wraps to the beginning of the buffer and continues down to the current line, if necessary. The second slash can be omitted if it ends a line. // repeats the last search.
• TODO ?re? - Searches for the previous line containing the regular expression re. The search wraps to the end of the buffer and continues up to the current line, if necessary. The second question mark can be omitted if it ends a line. ?? repeats the last search.
• TODO 'lc - Navigates to the line previously marked by a k (mark) command, where lc is a lowercase letter.

Commands

Editing Commands

• (.)a: Appends text to the buffer after the addressed line. Text is entered in input mode.
• (.,.)c: Changes lines in the buffer. The addressed lines are deleted, and text is appended in their place.
• (.,.)d: Deletes the addressed lines from the buffer.
• TODO e file: Edits the specified file and sets it as the default filename.
• TODO E file: Edits the specified file unconditionally, discarding any unsaved changes.

Display Commands

• (.,.)p: Prints the addressed lines.
• (.,.)n: Prints the addressed lines with their line numbers.
• TODO (.,.)l: Prints the addressed lines unambiguously.

File Operations

• f file: Sets or displays the default filename.
• (1,$)w file: Writes the addressed lines to the specified file, replacing the file's contents. (Only whole buffer)
• TODO (1,$)W file: Appends the addressed lines to the specified file.
• (1,$)wq file: Saves the addressed lines to a file and quits ed. (Only whole buffer)

Buffer Modification

• (.)i: Inserts text before the current line.
• (.)a: Appends text after the current line.
• (.,.)c: Prompts for input and replaces the addressed lines.
• (.,.)d: Deletes line range.
• TODO (.,+)j: Joins the addressed lines into a single line.
• TODO (.,.)m(.): Moves the addressed lines to the specified destination address.
• TODO (.,.)t(.): Copies the addressed lines to the specified destination address.

Search and Replace

• TODO (.,.)s/re/replacement/: Performs substitution on the addressed lines.
• TODO (1,$)g/re/command-list: Executes commands on lines matching a regex.
• TODO (1,$)v/re/command-list: Applies command-list to lines not matching the regex.

Regular Expressions

• Regular expressions are used to match patterns in text.

Miscellaneous Commands

• TODO H: Toggles the printing of error explanations.
• TODO (+)zn: Scrolls n lines at a time starting at addressed line.
• TODO ($)=: Prints the line number of the current or specified line.
• TODO !command: Executes the specified command via the shell.

Exiting Commands

• q: Quits ed, prompting if there are unsaved changes.
• TODO Q: Quits ed immediately without prompting for unsaved changes.