readline

The readline module provides an interface for reading input line by line from a readable stream (such as process.stdin). Supports prompts, history, and question/answer patterns.

API Surface

Interface

• readline.createInterface(options) — create interface.
  Options:
  • input: readable stream (e.g., process.stdin)
  • output: writable stream (e.g., process.stdout)
  • prompt: prompt string

Methods

• rl.question(query, cb) — ask question, call cb with answer.
• rl.prompt() — display prompt.
• rl.close() — close interface.

Events

• 'line' — emitted when user enters a line.
• 'close' — when input closes.
• 'SIGINT' — on Ctrl+C.

Examples (English only)

const readline = require("readline");

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: "> "
});

rl.prompt();

rl.on("line", (line) => {
  console.log("You typed:", line);
  if (line === "exit") rl.close();
  else rl.prompt();
});

rl.on("close", () => {
  console.log("Goodbye!");
  process.exit(0);
});

// Ask a single question
// rl.question("What is your name? ", (answer) => {
//   console.log("Hello", answer);
//   rl.close();
// });

Notes

• Use question for simple one-time input.
• Use line event with prompt for interactive shells.
• Always call close when done to free resources.
• Handle SIGINT (Ctrl+C) if you need graceful shutdown.