Rustyline is a readline implementation in Rust, inspired by Python's readline. It provides line editing functionality with history and completion support, making it useful for building command-line interfaces and interactive shells in Rust applications.

Pros

• Written in pure Rust, offering memory safety and performance benefits
• Supports cross-platform functionality (Windows, macOS, Linux)
• Provides customizable key bindings and completion behavior
• Actively maintained with regular updates and improvements

Cons

• May have a steeper learning curve compared to simpler input libraries
• Documentation could be more comprehensive for advanced use cases
• Limited to command-line applications, not suitable for GUI environments
• Some features may not be as mature as long-standing C libraries like GNU Readline

Code Examples

1. Basic usage:

use rustyline::error::ReadlineError;
use rustyline::Editor;

fn main() {
    let mut rl = Editor::<()>::new();
    loop {
        let readline = rl.readline(">> ");
        match readline {
            Ok(line) => {
                println!("Line: {}", line);
                rl.add_history_entry(line.as_str());
            },
            Err(ReadlineError::Interrupted) => {
                println!("CTRL-C");
                break
            },
            Err(ReadlineError::Eof) => {
                println!("CTRL-D");
                break
            },
            Err(err) => {
                println!("Error: {:?}", err);
                break
            }
        }
    }
}

2. Using custom completion:

use rustyline::completion::{Completer, Pair};
use rustyline::Context;
use rustyline::Editor;

struct MyCompleter;

impl Completer for MyCompleter {
    type Candidate = Pair;

    fn complete(&self, line: &str, pos: usize, _ctx: &Context<'_>) -> Result<(usize, Vec<Pair>), ReadlineError> {
        let commands = vec!["help", "quit", "list"];
        let matches: Vec<Pair> = commands
            .iter()
            .filter(|cmd| cmd.starts_with(line))
            .map(|cmd| Pair {
                display: cmd.to_string(),
                replacement: cmd.to_string(),
            })
            .collect();
        Ok((0, matches))
    }
}

fn main() {
    let mut rl = Editor::new();
    rl.set_completer(Some(MyCompleter));
    // ... rest of the code
}

3. Customizing key bindings:

use rustyline::config::Config;
use rustyline::Editor;
use rustyline::KeyEvent;
use rustyline::KeyCode;
use rustyline::Modifiers;

fn main() {
    let config = Config::builder()
        .keyseq_timeout(0)
        .edit_mode(rustyline::EditMode::Emacs)
        .build();
    let mut rl = Editor::with_config(config);
    
    rl.bind_sequence(KeyEvent(KeyCode::Char('f'), Modifiers::CTRL), rustyline::Cmd::ForwardChar);
    rl.bind_sequence(KeyEvent(KeyCode::Char('b'), Modifiers::CTRL), rustyline::Cmd::BackwardChar);
    
    // ... rest of the code
}

Getting Started

To use Rustyline in your Rust project, add the following to your Cargo.toml:

[dependencies]
rustyline = "10.0.0"

Then, in your Rust code:

use rustyline::error::ReadlineError;
use rustyline::Editor;

fn main() {
    let mut rl = Editor::<()>::new();
    if rl.readline(">> ").is_ok() {
        println!("It works!");
    }
}

This basic example sets up Rustyline and prompts the user for input.