Crate reedline

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§reedline \|/

§A readline replacement written in Rust

Reedline is a project to create a line editor (like bash’s readline or zsh’s zle) that supports many of the modern conveniences of CLIs, including syntax highlighting, completions, multiline support, Unicode support, and more. It is currently primarily developed as the interactive editor for nushell (starting with v0.60) striving to provide a pleasant interactive experience.

§Basic example

// Create a default reedline object to handle user input

use reedline::{DefaultPrompt, Reedline, Signal};

let mut line_editor = Reedline::create();
let prompt = DefaultPrompt::default();

loop {
    let sig = line_editor.read_line(&prompt);
    match sig {
        Ok(Signal::Success(buffer)) => {
            println!("We processed: {}", buffer);
        Ok(Signal::CtrlD) | Ok(Signal::CtrlC) => {
        x => {
            println!("Event: {:?}", x);

§Integrate with custom keybindings

// Configure reedline with custom keybindings

//    [dependencies]
//    crossterm = "*"

use {
  crossterm::event::{KeyCode, KeyModifiers},
  reedline::{default_emacs_keybindings, EditCommand, Reedline, Emacs, ReedlineEvent},

let mut keybindings = default_emacs_keybindings();
let edit_mode = Box::new(Emacs::new(keybindings));

let mut line_editor = Reedline::create().with_edit_mode(edit_mode);

§Integrate with History

// Create a reedline object with history support, including history size limits

use reedline::{FileBackedHistory, Reedline};

let history = Box::new(
    FileBackedHistory::with_file(5, "history.txt".into())
        .expect("Error configuring history with file"),
let mut line_editor = Reedline::create()

§Integrate with custom syntax Highlighter

// Create a reedline object with highlighter support

use reedline::{ExampleHighlighter, Reedline};

let commands = vec![
  "hello world".into(),
  "hello world reedline".into(),
  "this is the reedline crate".into(),
let mut line_editor =

§Integrate with custom tab completion

// Create a reedline object with tab completions support

use reedline::{default_emacs_keybindings, ColumnarMenu, DefaultCompleter, Emacs, KeyCode, KeyModifiers, Reedline, ReedlineEvent, ReedlineMenu, MenuBuilder};

let commands = vec![
  "hello world".into(),
  "hello world reedline".into(),
  "this is the reedline crate".into(),
let completer = Box::new(DefaultCompleter::new_with_wordlen(commands.clone(), 2));
// Use the interactive menu to select options from the completer
let completion_menu = Box::new(ColumnarMenu::default().with_name("completion_menu"));
// Set up the required keybindings
let mut keybindings = default_emacs_keybindings();

let edit_mode = Box::new(Emacs::new(keybindings));

let mut line_editor = Reedline::create()

§Integrate with Hinter for fish-style history autosuggestions

// Create a reedline object with in-line hint support

//    [dependencies]
//    nu-ansi-term = "*"

use {
  nu_ansi_term::{Color, Style},
  reedline::{DefaultHinter, Reedline},

let mut line_editor = Reedline::create().with_hinter(Box::new(

§Integrate with custom line completion Validator

// Create a reedline object with line completion validation support

use reedline::{DefaultValidator, Reedline};

let validator = Box::new(DefaultValidator);

let mut line_editor = Reedline::create().with_validator(validator);

§Use custom EditMode

// Create a reedline object with custom edit mode
// This can define a keybinding setting or enable vi-emulation
use reedline::{
    default_vi_insert_keybindings, default_vi_normal_keybindings, EditMode, Reedline, Vi,

let mut line_editor = Reedline::create().with_edit_mode(Box::new(Vi::new(

§Crate features

  • clipboard: Enable support to use the SystemClipboard. Enabling this feature will return a SystemClipboard instead of a local clipboard when calling get_default_clipboard().
  • bashisms: Enable support for special text sequences that recall components from the history. e.g. !! and !$. For use in shells like bash or nushell.
  • sqlite: Provides the SqliteBackedHistory to store richer information in the history. Statically links the required sqlite version.
  • sqlite-dynlib: Alternative to the feature sqlite. Will not statically link. Requires sqlite >= 3.38 to link dynamically!
  • external_printer: Experimental: Thread-safe ExternalPrinter handle to print lines from concurrently running threads.

§Are we prompt yet? (Development status)

Nushell has now all the basic features to become the primary line editor for nushell

  • General editing functionality, that should feel familiar coming from other shells (e.g. bash, fish, zsh).
  • Configurable keybindings (emacs-style bindings and basic vi-style).
  • Configurable prompt
  • Content-aware syntax highlighting.
  • Autocompletion (With graphical selection menu or simple cycling inline).
  • History with interactive search options (optionally persists to file, can support multilple sessions accessing the same file)
  • Fish-style history autosuggestion hints
  • Undo support.
  • Clipboard integration
  • Line completeness validation for seamless entry of multiline command sequences.

§Areas for future improvements

  • Support for Unicode beyond simple left-to-right scripts
  • Easier keybinding configuration
  • Support for more advanced vi commands
  • Visual selection
  • Smooth experience if completion or prompt content takes long to compute
  • Support for a concurrent output stream from background tasks to be displayed, while the input prompt is active. (“Full duplex” mode)

For more ideas check out the feature discussion or hop on the #reedline channel of the nushell discord.

§Development history

If you want to follow along with the history how reedline got started, you can watch the recordings of JT’s live-coding streams.

Playlist: Creating a line editor in Rust


For currently more mature Rust line editing check out:


  • Collection of common functions that can be used to create menus


  • Menu to present suggestions in a columnar fashion It presents a description of the suggestion if available
  • Maps cursor shapes to each edit mode (emacs, vi normal & vi insert). If any of the fields is None, the cursor won’t get changed by Reedline for that mode.
  • A hinter that uses the completions or the history to show a hint to the user
  • A default completer that can detect keywords
  • A hinter that uses the completions or the history to show a hint to the user
  • Simple Prompt displaying a configurable left and a right prompt. For more fine-tuned configuration, implement the Prompt trait. For the default configuration, use DefaultPrompt::default()
  • A default validator which checks for mismatched quotes and brackets
  • Completion menu definition
  • Stateful editor executing changes to the underlying LineBuffer
  • This parses the incoming Events like a emacs style-editor
  • A simple, example highlighter that shows how to highlight keywords
  • An ExternalPrinter allows to print messages of text while editing a line. The message is printed as a new line, the line-edit will continue below the output.
  • Stateful history that allows up/down-arrow browsing with an internal cursor.
  • Represents one run command with some optional additional context
  • Unique ID for the HistoryItem. More recent items have higher ids than older ones.
  • Unique ID for the session in which reedline was run to disambiguate different sessions
  • Menu to present suggestions like similar to Ide completion menus
  • Represents key modifiers (shift, control, alt, etc.).
  • Main definition of editor keybindings
  • In memory representation of the entered line(s) including a cursor position to facilitate cursor based editing.
  • Struct to store the menu style Context menu definition
  • Struct to store the menu style
  • Implementation of the output to the terminal
  • A representation of the history search
  • Line editor engine
  • separate struct to not expose anything to the public (for now)
  • A simple wrapper for crossterm::event::Event
  • Defines additional filters for querying the History
  • Query for search in the potentially rich History
  • Highlight all matches for a given search string in a line
  • A span of source code, with positions in bytes
  • A history that stores the values to an SQLite database. In addition to storing the command, the history can store an additional arbitrary HistoryEntryContext, to add information such as a timestamp, running directory, result…
  • A representation of a buffer with styling, used for doing syntax highlighting
  • Suggestion returned by the Completer
  • This parses incoming input Events like a Vi-Style editor




  • A trait that defines how to convert some text and a position to a list of potential completions in that position. The text could be a part of the whole line, and the position is the index of the end of the text in the original line.
  • Define the style of parsing for the edit events Available default options:
  • The syntax highlighting trait. Implementers of this trait will take in the current string and then return a StyledText object, which represents the contents of the original line as styled strings
  • A trait that’s responsible for returning the hint for the current line and position Hints are often shown in-line as part of the buffer, showing the user text they can accept or ignore
  • Represents a history file or database Data could be stored e.g. in a plain text file, in a JSONL file, in a SQLite database
  • Trait that defines how a menu will be printed by the painter
  • Common builder for all menus
  • API to provide a custom prompt.
  • The syntax validation trait. Implementers of this trait will check to see if the current input is incomplete and spans multiple lines


Type Aliases§