TTY | Node.js v8.3.0 Documentation

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# TTY#

    Stability: 2 - Stable

The `tty` module provides the `tty.ReadStream` and `tty.WriteStream` classes. In most cases, it will not be necessary or possible to use this module directly. However, it can be accessed using:

    const tty = require('tty');

When Node.js detects that it is being run inside a text terminal ("TTY") context, the `process.stdin` will, by default, be initialized as an instance of `tty.ReadStream` and both `process.stdout` and `process.stderr` will, by default be instances of `tty.WriteStream`. The preferred method of determining whether Node.js is being run within a TTY context is to check that the value of the `process.stdout.isTTY` property is `true`:

    $ node -p -e "Boolean(process.stdout.isTTY)"
    true
    $ node -p -e "Boolean(process.stdout.isTTY)" | cat
    false

In most cases, there should be little to no reason for an application to create instances of the `tty.ReadStream` and `tty.WriteStream` classes.

## Class: tty.ReadStream#

Added in: v0.5.8

The `tty.ReadStream` class is a subclass of `net.Socket` that represents the readable side of a TTY. In normal circumstances `process.stdin` will be the only `tty.ReadStream` instance in a Node.js process and there should be no reason to create additional instances.

### readStream.isRaw#

Added in: v0.7.7

A `boolean` that is `true` if the TTY is currently configured to operate as a raw device. Defaults to `false`.

### readStream.setRawMode(mode)#

Added in: v0.7.7

Allows configuration of `tty.ReadStream` so that it operates as a raw device.

When in raw mode, input is always available character-by-character, not including modifiers. Additionally, all special processing of characters by the terminal is disabled, including echoing input characters. Note that `CTRL`+`C` will no longer cause a `SIGINT` when in this mode.

- `mode` <boolean> If `true`, configures the `tty.ReadStream` to operate as a raw device. If `false`, configures the `tty.ReadStream` to operate in its default mode. The `readStream.isRaw` property will be set to the resulting mode.

## Class: tty.WriteStream#

Added in: v0.5.8

The `tty.WriteStream` class is a subclass of `net.Socket` that represents the writable side of a TTY. In normal circumstances, `process.stdout` and `process.stderr` will be the only `tty.WriteStream` instances created for a Node.js process and there should be no reason to create additional instances.

### Event: 'resize'#

Added in: v0.7.7

The `'resize'` event is emitted whenever either of the `writeStream.columns` or `writeStream.rows` properties have changed. No arguments are passed to the listener callback when called.

    process.stdout.on('resize', () => {
      console.log('screen size has changed!');
      console.log(`${process.stdout.columns}x${process.stdout.rows}`);
    });

Note: On Windows resize events will be emitted only if stdin is unpaused (by a call to `resume()` or by adding a data listener) and in raw mode. It can also be triggered if a terminal control sequence that moves the cursor is written to the screen. Also, the resize event will only be signaled if the console screen buffer height was also changed. For example shrinking the console window height will not cause the resize event to be emitted. Increasing the console window height will only be registered when the new console window height is greater than the current console buffer size.

### writeStream.columns#

Added in: v0.7.7

A `number` specifying the number of columns the TTY currently has. This property is updated whenever the `'resize'` event is emitted.

### writeStream.rows#

Added in: v0.7.7

A `number` specifying the number of rows the TTY currently has. This property is updated whenever the `'resize'` event is emitted.

## tty.isatty(fd)#

Added in: v0.5.8

- `fd` <number> A numeric file descriptor

The `tty.isatty()` method returns `true` if the given `fd` is associated with a TTY and `false` if is not.