readline

• class Interface

  Instances of the readline.Interface class are constructed using the readline.createInterface() method. Every instance is associated with a single input Readable stream and a single output Writable stream. The output stream is used to print prompts for user input that arrives on, and is read from, the input stream.

  • readonly cursor: number

    The cursor position relative to rl.line.

    This will track where the current cursor lands in the input string, when reading input from a TTY stream. The position of cursor determines the portion of the input string that will be modified as input is processed, as well as the column where the terminal caret will be rendered.

  • readonly line: string

    The current input data being processed by node.

    This can be used when collecting input from a TTY stream to retrieve the current value that has been processed thus far, prior to the line event being emitted. Once the line event has been emitted, this property will be an empty string.

    Be aware that modifying the value during the instance runtime may have unintended consequences if rl.cursor is not also controlled.

    If not using a TTY stream for input, use the 'line' event.

    One possible use case would be as follows:

    const values = ['lorem ipsum', 'dolor sit amet'];
    const rl = readline.createInterface(process.stdin);
    const showResults = debounce(() => {
      console.log(
        '\n',
        values.filter((val) => val.startsWith(rl.line)).join(' '),
      );
    }, 300);
    process.stdin.on('keypress', (c, k) => {
      showResults();
    });
    
  • readonly terminal: boolean
  • [Symbol.asyncIterator](): AsyncIterator<string>;
  • [events.captureRejectionSymbol](

    error: Error,

    event: string | symbol,

    ...args: any[]

    ): void;

    The Symbol.for('nodejs.rejection') method is called in case a promise rejection happens when emitting an event and captureRejections is enabled on the emitter. It is possible to use events.captureRejectionSymbol in place of Symbol.for('nodejs.rejection').

    import { EventEmitter, captureRejectionSymbol } from 'node:events';
    
    class MyClass extends EventEmitter {
      constructor() {
        super({ captureRejections: true });
      }
    
      [captureRejectionSymbol](err, event, ...args) {
        console.log('rejection happened for', event, 'with', err, ...args);
        this.destroy(err);
      }
    
      destroy(err) {
        // Tear the resource down here.
      }
    }
    
  • [Symbol.dispose](): void;

    Alias for rl.close().

  • addListener<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener: (...args: InterfaceEventMap[E]) => void

    ): this;

    Alias for emitter.on(eventName, listener).

    addListener(

    eventName: string | symbol,

    listener: (...args: any[]) => void

    ): this;

    Alias for emitter.on(eventName, listener).
  • close(): void;

    The rl.close() method closes the Interface instance and relinquishes control over the input and output streams. When called, the 'close' event will be emitted.

    Calling rl.close() does not immediately stop other events (including 'line') from being emitted by the Interface instance.

  • emit<E extends keyof InterfaceEventMap>(

    eventName: E,

    ...args: InterfaceEventMap[E]

    ): boolean;

    Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

    Returns true if the event had listeners, false otherwise.

    import { EventEmitter } from 'node:events';
    const myEmitter = new EventEmitter();
    
    // First listener
    myEmitter.on('event', function firstListener() {
      console.log('Helloooo! first listener');
    });
    // Second listener
    myEmitter.on('event', function secondListener(arg1, arg2) {
      console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
    });
    // Third listener
    myEmitter.on('event', function thirdListener(...args) {
      const parameters = args.join(', ');
      console.log(`event with parameters ${parameters} in third listener`);
    });
    
    console.log(myEmitter.listeners('event'));
    
    myEmitter.emit('event', 1, 2, 3, 4, 5);
    
    // Prints:
    // [
    //   [Function: firstListener],
    //   [Function: secondListener],
    //   [Function: thirdListener]
    // ]
    // Helloooo! first listener
    // event with parameters 1, 2 in second listener
    // event with parameters 1, 2, 3, 4, 5 in third listener
    

    emit(

    eventName: string | symbol,

    ...args: any[]

    ): boolean;

    Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

    Returns true if the event had listeners, false otherwise.

    import { EventEmitter } from 'node:events';
    const myEmitter = new EventEmitter();
    
    // First listener
    myEmitter.on('event', function firstListener() {
      console.log('Helloooo! first listener');
    });
    // Second listener
    myEmitter.on('event', function secondListener(arg1, arg2) {
      console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
    });
    // Third listener
    myEmitter.on('event', function thirdListener(...args) {
      const parameters = args.join(', ');
      console.log(`event with parameters ${parameters} in third listener`);
    });
    
    console.log(myEmitter.listeners('event'));
    
    myEmitter.emit('event', 1, 2, 3, 4, 5);
    
    // Prints:
    // [
    //   [Function: firstListener],
    //   [Function: secondListener],
    //   [Function: thirdListener]
    // ]
    // Helloooo! first listener
    // event with parameters 1, 2 in second listener
    // event with parameters 1, 2, 3, 4, 5 in third listener
    
  • eventNames(): string | symbol[];

    Returns an array listing the events for which the emitter has registered listeners.

    import { EventEmitter } from 'node:events';
    
    const myEE = new EventEmitter();
    myEE.on('foo', () => {});
    myEE.on('bar', () => {});
    
    const sym = Symbol('symbol');
    myEE.on(sym, () => {});
    
    console.log(myEE.eventNames());
    // Prints: [ 'foo', 'bar', Symbol(symbol) ]
    
  • getCursorPos(): CursorPos;

    Returns the real position of the cursor in relation to the input prompt + string. Long input (wrapping) strings, as well as multiple line prompts are included in the calculations.

  • getMaxListeners(): number;

    Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to events.defaultMaxListeners.

  • getPrompt(): string;

    The rl.getPrompt() method returns the current prompt used by rl.prompt().

    @returns

    the current prompt string

  • listenerCount<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener?: (...args: InterfaceEventMap[E]) => void

    ): number;

    Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

    @param eventName

    The name of the event being listened for

    @param listener

    The event handler function

    listenerCount(

    eventName: string | symbol,

    listener?: (...args: any[]) => void

    ): number;

    Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

    @param eventName

    The name of the event being listened for

    @param listener

    The event handler function

  • listeners<E extends keyof InterfaceEventMap>(

    eventName: E

    ): (...args: InterfaceEventMap[E]) => void[];

    Returns a copy of the array of listeners for the event named eventName.

    server.on('connection', (stream) => {
      console.log('someone connected!');
    });
    console.log(util.inspect(server.listeners('connection')));
    // Prints: [ [Function] ]
    

    listeners(

    eventName: string | symbol

    ): (...args: any[]) => void[];

    Returns a copy of the array of listeners for the event named eventName.

    server.on('connection', (stream) => {
      console.log('someone connected!');
    });
    console.log(util.inspect(server.listeners('connection')));
    // Prints: [ [Function] ]
    
  • off<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener: (...args: InterfaceEventMap[E]) => void

    ): this;

    Alias for emitter.removeListener().

    off(

    eventName: string | symbol,

    listener: (...args: any[]) => void

    ): this;

    Alias for emitter.removeListener().
  • on<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener: (...args: InterfaceEventMap[E]) => void

    ): this;

    Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.on('connection', (stream) => {
      console.log('someone connected!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.on('foo', () => console.log('a'));
    myEE.prependListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    //   b
    //   a
    

    @param eventName

    The name of the event.

    @param listener

    The callback function

    on(

    eventName: string | symbol,

    listener: (...args: any[]) => void

    ): this;

    Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.on('connection', (stream) => {
      console.log('someone connected!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.on('foo', () => console.log('a'));
    myEE.prependListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    //   b
    //   a
    

    @param eventName

    The name of the event.

    @param listener

    The callback function

  • once<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener: (...args: InterfaceEventMap[E]) => void

    ): this;

    Adds a one-time listener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

    server.once('connection', (stream) => {
      console.log('Ah, we have our first user!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.once('foo', () => console.log('a'));
    myEE.prependOnceListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    //   b
    //   a
    

    @param eventName

    The name of the event.

    @param listener

    The callback function

    once(

    eventName: string | symbol,

    listener: (...args: any[]) => void

    ): this;

    Adds a one-time listener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

    server.once('connection', (stream) => {
      console.log('Ah, we have our first user!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.once('foo', () => console.log('a'));
    myEE.prependOnceListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    //   b
    //   a
    

    @param eventName

    The name of the event.

    @param listener

    The callback function

  • pause(): this;

    The rl.pause() method pauses the input stream, allowing it to be resumed later if necessary.

    Calling rl.pause() does not immediately pause other events (including 'line') from being emitted by the Interface instance.

  • prependListener<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener: (...args: InterfaceEventMap[E]) => void

    ): this;

    Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.prependListener('connection', (stream) => {
      console.log('someone connected!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    @param eventName

    The name of the event.

    @param listener

    The callback function

    prependListener(

    eventName: string | symbol,

    listener: (...args: any[]) => void

    ): this;

    Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.prependListener('connection', (stream) => {
      console.log('someone connected!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    @param eventName

    The name of the event.

    @param listener

    The callback function

  • prependOnceListener<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener: (...args: InterfaceEventMap[E]) => void

    ): this;

    Adds a one-time listener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

    server.prependOnceListener('connection', (stream) => {
      console.log('Ah, we have our first user!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    @param eventName

    The name of the event.

    @param listener

    The callback function

    prependOnceListener(

    eventName: string | symbol,

    listener: (...args: any[]) => void

    ): this;

    Adds a one-time listener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

    server.prependOnceListener('connection', (stream) => {
      console.log('Ah, we have our first user!');
    });
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    @param eventName

    The name of the event.

    @param listener

    The callback function

  • prompt(

    preserveCursor?: boolean

    ): void;

    The rl.prompt() method writes the Interface instances configuredprompt to a new line in output in order to provide a user with a new location at which to provide input.

    When called, rl.prompt() will resume the input stream if it has been paused.

    If the Interface was created with output set to null or undefined the prompt is not written.

    @param preserveCursor

    If true, prevents the cursor placement from being reset to 0.

  • question(

    query: string,

    callback: (answer: string) => void

    ): void;

    The rl.question() method displays the query by writing it to the output, waits for user input to be provided on input, then invokes the callback function passing the provided input as the first argument.

    When called, rl.question() will resume the input stream if it has been paused.

    If the Interface was created with output set to null or undefined the query is not written.

    The callback function passed to rl.question() does not follow the typical pattern of accepting an Error object or null as the first argument. The callback is called with the provided answer as the only argument.

    An error will be thrown if calling rl.question() after rl.close().

    Example usage:

    rl.question('What is your favorite food? ', (answer) => {
      console.log(`Oh, so your favorite food is ${answer}`);
    });
    

    Using an AbortController to cancel a question.

    const ac = new AbortController();
    const signal = ac.signal;
    
    rl.question('What is your favorite food? ', { signal }, (answer) => {
      console.log(`Oh, so your favorite food is ${answer}`);
    });
    
    signal.addEventListener('abort', () => {
      console.log('The food question timed out');
    }, { once: true });
    
    setTimeout(() => ac.abort(), 10000);
    

    @param query

    A statement or query to write to output, prepended to the prompt.

    @param callback

    A callback function that is invoked with the user's input in response to the query.

    question(

    query: string,

    options: Abortable,

    callback: (answer: string) => void

    ): void;

    The rl.question() method displays the query by writing it to the output, waits for user input to be provided on input, then invokes the callback function passing the provided input as the first argument.

    When called, rl.question() will resume the input stream if it has been paused.

    If the Interface was created with output set to null or undefined the query is not written.

    The callback function passed to rl.question() does not follow the typical pattern of accepting an Error object or null as the first argument. The callback is called with the provided answer as the only argument.

    An error will be thrown if calling rl.question() after rl.close().

    Example usage:

    rl.question('What is your favorite food? ', (answer) => {
      console.log(`Oh, so your favorite food is ${answer}`);
    });
    

    Using an AbortController to cancel a question.

    const ac = new AbortController();
    const signal = ac.signal;
    
    rl.question('What is your favorite food? ', { signal }, (answer) => {
      console.log(`Oh, so your favorite food is ${answer}`);
    });
    
    signal.addEventListener('abort', () => {
      console.log('The food question timed out');
    }, { once: true });
    
    setTimeout(() => ac.abort(), 10000);
    

    @param query

    A statement or query to write to output, prepended to the prompt.

    @param callback

    A callback function that is invoked with the user's input in response to the query.

  • rawListeners<E extends keyof InterfaceEventMap>(

    eventName: E

    ): (...args: InterfaceEventMap[E]) => void[];

    Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

    import { EventEmitter } from 'node:events';
    const emitter = new EventEmitter();
    emitter.once('log', () => console.log('log once'));
    
    // Returns a new Array with a function `onceWrapper` which has a property
    // `listener` which contains the original listener bound above
    const listeners = emitter.rawListeners('log');
    const logFnWrapper = listeners[0];
    
    // Logs "log once" to the console and does not unbind the `once` event
    logFnWrapper.listener();
    
    // Logs "log once" to the console and removes the listener
    logFnWrapper();
    
    emitter.on('log', () => console.log('log persistently'));
    // Will return a new Array with a single function bound by `.on()` above
    const newListeners = emitter.rawListeners('log');
    
    // Logs "log persistently" twice
    newListeners[0]();
    emitter.emit('log');
    

    rawListeners(

    eventName: string | symbol

    ): (...args: any[]) => void[];

    Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

    import { EventEmitter } from 'node:events';
    const emitter = new EventEmitter();
    emitter.once('log', () => console.log('log once'));
    
    // Returns a new Array with a function `onceWrapper` which has a property
    // `listener` which contains the original listener bound above
    const listeners = emitter.rawListeners('log');
    const logFnWrapper = listeners[0];
    
    // Logs "log once" to the console and does not unbind the `once` event
    logFnWrapper.listener();
    
    // Logs "log once" to the console and removes the listener
    logFnWrapper();
    
    emitter.on('log', () => console.log('log persistently'));
    // Will return a new Array with a single function bound by `.on()` above
    const newListeners = emitter.rawListeners('log');
    
    // Logs "log persistently" twice
    newListeners[0]();
    emitter.emit('log');
    
  • removeAllListeners<E extends keyof InterfaceEventMap>(

    eventName?: E

    ): this;

    Removes all listeners, or those of the specified eventName.

    It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

    Returns a reference to the EventEmitter, so that calls can be chained.

    removeAllListeners(

    eventName?: string | symbol

    ): this;

    Removes all listeners, or those of the specified eventName.

    It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

    Returns a reference to the EventEmitter, so that calls can be chained.
  • removeListener<E extends keyof InterfaceEventMap>(

    eventName: E,

    listener: (...args: InterfaceEventMap[E]) => void

    ): this;

    Removes the specified listener from the listener array for the event named eventName.

    const callback = (stream) => {
      console.log('someone connected!');
    };
    server.on('connection', callback);
    // ...
    server.removeListener('connection', callback);
    

    removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

    Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() in progress. Subsequent events behave as expected.

    import { EventEmitter } from 'node:events';
    class MyEmitter extends EventEmitter {}
    const myEmitter = new MyEmitter();
    
    const callbackA = () => {
      console.log('A');
      myEmitter.removeListener('event', callbackB);
    };
    
    const callbackB = () => {
      console.log('B');
    };
    
    myEmitter.on('event', callbackA);
    
    myEmitter.on('event', callbackB);
    
    // callbackA removes listener callbackB but it will still be called.
    // Internal listener array at time of emit [callbackA, callbackB]
    myEmitter.emit('event');
    // Prints:
    //   A
    //   B
    
    // callbackB is now removed.
    // Internal listener array [callbackA]
    myEmitter.emit('event');
    // Prints:
    //   A
    

    Because listeners are managed using an internal array, calling this will change the position indexes of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

    When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping') listener is removed:

    import { EventEmitter } from 'node:events';
    const ee = new EventEmitter();
    
    function pong() {
      console.log('pong');
    }
    
    ee.on('ping', pong);
    ee.once('ping', pong);
    ee.removeListener('ping', pong);
    
    ee.emit('ping');
    ee.emit('ping');
    

    Returns a reference to the EventEmitter, so that calls can be chained.

    removeListener(

    eventName: string | symbol,

    listener: (...args: any[]) => void

    ): this;

    Removes the specified listener from the listener array for the event named eventName.

    const callback = (stream) => {
      console.log('someone connected!');
    };
    server.on('connection', callback);
    // ...
    server.removeListener('connection', callback);
    

    removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

    Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() in progress. Subsequent events behave as expected.

    import { EventEmitter } from 'node:events';
    class MyEmitter extends EventEmitter {}
    const myEmitter = new MyEmitter();
    
    const callbackA = () => {
      console.log('A');
      myEmitter.removeListener('event', callbackB);
    };
    
    const callbackB = () => {
      console.log('B');
    };
    
    myEmitter.on('event', callbackA);
    
    myEmitter.on('event', callbackB);
    
    // callbackA removes listener callbackB but it will still be called.
    // Internal listener array at time of emit [callbackA, callbackB]
    myEmitter.emit('event');
    // Prints:
    //   A
    //   B
    
    // callbackB is now removed.
    // Internal listener array [callbackA]
    myEmitter.emit('event');
    // Prints:
    //   A
    

    Because listeners are managed using an internal array, calling this will change the position indexes of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

    When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping') listener is removed:

    import { EventEmitter } from 'node:events';
    const ee = new EventEmitter();
    
    function pong() {
      console.log('pong');
    }
    
    ee.on('ping', pong);
    ee.once('ping', pong);
    ee.removeListener('ping', pong);
    
    ee.emit('ping');
    ee.emit('ping');
    

    Returns a reference to the EventEmitter, so that calls can be chained.
  • resume(): this;

    The rl.resume() method resumes the input stream if it has been paused.

  • setMaxListeners(

    n: number

    ): this;

    By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

    Returns a reference to the EventEmitter, so that calls can be chained.
  • setPrompt(

    prompt: string

    ): void;

    The rl.setPrompt() method sets the prompt that will be written to output whenever rl.prompt() is called.
  • write(

    data: string | Buffer<ArrayBufferLike>,

    key?: Key

    ): void;

    The rl.write() method will write either data or a key sequence identified by key to the output. The key argument is supported only if output is a TTY text terminal. See TTY keybindings for a list of key combinations.

    If key is specified, data is ignored.

    When called, rl.write() will resume the input stream if it has been paused.

    If the Interface was created with output set to null or undefined the data and key are not written.

    rl.write('Delete this!');
    // Simulate Ctrl+U to delete the line written previously
    rl.write(null, { ctrl: true, name: 'u' });
    

    The rl.write() method will write the data to the readline Interface's input as if it were provided by the user.

    write(

    data: undefined | null | string | Buffer<ArrayBufferLike>,

    key: Key

    ): void;

    The rl.write() method will write either data or a key sequence identified by key to the output. The key argument is supported only if output is a TTY text terminal. See TTY keybindings for a list of key combinations.

    If key is specified, data is ignored.

    When called, rl.write() will resume the input stream if it has been paused.

    If the Interface was created with output set to null or undefined the data and key are not written.

    rl.write('Delete this!');
    // Simulate Ctrl+U to delete the line written previously
    rl.write(null, { ctrl: true, name: 'u' });
    

    The rl.write() method will write the data to the readline Interface's input as if it were provided by the user.
• function clearLine(

  stream: WritableStream,

  dir: Direction,

  callback?: () => void

  ): boolean;

  The readline.clearLine() method clears current line of given TTY stream in a specified direction identified by dir.

  @param callback

  Invoked once the operation completes.

  @returns

  false if stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

• function clearScreenDown(

  stream: WritableStream,

  callback?: () => void

  ): boolean;

  The readline.clearScreenDown() method clears the given TTY stream from the current position of the cursor down.

  @param callback

  Invoked once the operation completes.

  @returns

  false if stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

• function createInterface(

  input: ReadableStream,

  output?: WritableStream,

  completer?: Completer | AsyncCompleter,

  terminal?: boolean

  ): Interface;

  The readline.createInterface() method creates a new readline.Interface instance.

  import readline from 'node:readline';
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });
  

  Once the readline.Interface instance is created, the most common case is to listen for the 'line' event:

  rl.on('line', (line) => {
    console.log(`Received: ${line}`);
  });
  

  If terminal is true for this instance then the output stream will get the best compatibility if it defines an output.columns property and emits a 'resize' event on the output if or when the columns ever change (process.stdout does this automatically when it is a TTY).

  When creating a readline.Interface using stdin as input, the program will not terminate until it receives an EOF character. To exit without waiting for user input, call process.stdin.unref().

  function createInterface(

  options: ReadLineOptions

  ): Interface;

  The readline.createInterface() method creates a new readline.Interface instance.

  import readline from 'node:readline';
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });
  

  Once the readline.Interface instance is created, the most common case is to listen for the 'line' event:

  rl.on('line', (line) => {
    console.log(`Received: ${line}`);
  });
  

  If terminal is true for this instance then the output stream will get the best compatibility if it defines an output.columns property and emits a 'resize' event on the output if or when the columns ever change (process.stdout does this automatically when it is a TTY).

  When creating a readline.Interface using stdin as input, the program will not terminate until it receives an EOF character. To exit without waiting for user input, call process.stdin.unref().
• function cursorTo(

  stream: WritableStream,

  x: number,

  y?: number,

  callback?: () => void

  ): boolean;

  The readline.cursorTo() method moves cursor to the specified position in a given TTY stream.

  @param callback

  Invoked once the operation completes.

  @returns

  false if stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

• function emitKeypressEvents(

  stream: ReadableStream,

  readlineInterface?: Interface

  ): void;

  The readline.emitKeypressEvents() method causes the given Readable stream to begin emitting 'keypress' events corresponding to received input.

  Optionally, interface specifies a readline.Interface instance for which autocompletion is disabled when copy-pasted input is detected.

  If the stream is a TTY, then it must be in raw mode.

  This is automatically called by any readline instance on its input if the input is a terminal. Closing the readline instance does not stop the input from emitting 'keypress' events.

  readline.emitKeypressEvents(process.stdin);
  if (process.stdin.isTTY)
    process.stdin.setRawMode(true);
  

  Example: Tiny CLI

  The following example illustrates the use of readline.Interface class to implement a small command-line interface:

  import readline from 'node:readline';
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: 'OHAI> ',
  });
  
  rl.prompt();
  
  rl.on('line', (line) => {
    switch (line.trim()) {
      case 'hello':
        console.log('world!');
        break;
      default:
        console.log(`Say what? I might have heard '${line.trim()}'`);
        break;
    }
    rl.prompt();
  }).on('close', () => {
    console.log('Have a great day!');
    process.exit(0);
  });
  

  Example: Read file stream line-by-Line

  A common use case for readline is to consume an input file one line at a time. The easiest way to do so is leveraging the fs.ReadStream API as well as a for await...of loop:

  import fs from 'node:fs';
  import readline from 'node:readline';
  
  async function processLineByLine() {
    const fileStream = fs.createReadStream('input.txt');
  
    const rl = readline.createInterface({
      input: fileStream,
      crlfDelay: Infinity,
    });
    // Note: we use the crlfDelay option to recognize all instances of CR LF
    // ('\r\n') in input.txt as a single line break.
  
    for await (const line of rl) {
      // Each line in input.txt will be successively available here as `line`.
      console.log(`Line from file: ${line}`);
    }
  }
  
  processLineByLine();
  

  Alternatively, one could use the 'line' event:

  import fs from 'node:fs';
  import readline from 'node:readline';
  
  const rl = readline.createInterface({
    input: fs.createReadStream('sample.txt'),
    crlfDelay: Infinity,
  });
  
  rl.on('line', (line) => {
    console.log(`Line from file: ${line}`);
  });
  

  Currently, for await...of loop can be a bit slower. If async / await flow and speed are both essential, a mixed approach can be applied:

  import { once } from 'node:events';
  import { createReadStream } from 'node:fs';
  import { createInterface } from 'node:readline';
  
  (async function processLineByLine() {
    try {
      const rl = createInterface({
        input: createReadStream('big-file.txt'),
        crlfDelay: Infinity,
      });
  
      rl.on('line', (line) => {
        // Process the line.
      });
  
      await once(rl, 'close');
  
      console.log('File processed.');
    } catch (err) {
      console.error(err);
    }
  })();
  
• function moveCursor(

  stream: WritableStream,

  dx: number,

  dy: number,

  callback?: () => void

  ): boolean;

  The readline.moveCursor() method moves the cursor relative to its current position in a given TTY stream.

  @param callback

  Invoked once the operation completes.

  @returns

  false if stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

Type definitions

• interface CursorPos

  • cols: number
  • rows: number

• interface InterfaceEventMap

  • close: []
  • history: [history: string[]]
  • line: [input: string]
  • pause: []
  • resume: []
  • SIGCONT: []
  • SIGINT: []
  • SIGTSTP: []

• interface Key

  • ctrl?: boolean
  • meta?: boolean
  • name?: string
  • sequence?: string
  • shift?: boolean

• interface ReadLineOptions

  • completer?: Completer | AsyncCompleter

    An optional function used for Tab autocompletion.

  • crlfDelay?: number

    If the delay between \r and

    exceeds crlfDelay milliseconds, both \r and

    will be treated as separate end-of-line input. crlfDelay will be coerced to a number no less than 100. It can be set to Infinity, in which case \r followed by

    will always be considered a single newline (which may be reasonable for reading files with

    \r
    

    line delimiter).

  • escapeCodeTimeout?: number

    The duration readline will wait for a character (when reading an ambiguous key sequence in milliseconds one that can both form a complete key sequence using the input read so far and can take additional input to complete a longer key sequence).

  • history?: string[]

    Initial list of history lines. This option makes sense only if terminal is set to true by the user or by an internal output check, otherwise the history caching mechanism is not initialized at all.

  • historySize?: number

    Maximum number of history lines retained. To disable the history set this value to 0. This option makes sense only if terminal is set to true by the user or by an internal output check, otherwise the history caching mechanism is not initialized at all.

  • input: ReadableStream

    The Readable stream to listen to

  • output?: WritableStream

    The Writable stream to write readline data to.

  • prompt?: string

    The prompt string to use.

  • removeHistoryDuplicates?: boolean

    If true, when a new input line added to the history list duplicates an older one, this removes the older line from the list.

  • signal?: AbortSignal

    Allows closing the interface using an AbortSignal. Aborting the signal will internally call close on the interface.

  • tabSize?: number

    The number of spaces a tab is equal to (minimum 1).

  • terminal?: boolean

    true if the input and output streams should be treated like a TTY, and have ANSI/VT100 escape codes written to it. Default: checking isTTY on the output stream upon instantiation.

• type AsyncCompleter = (line: string, callback: (err?: null | Error, result?: CompleterResult) => void) => void
• type Completer = (line: string) => CompleterResult
• type CompleterResult = [string[], string]
• type Direction = -1 | 0 | 1
• type ReadLine = Interface