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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.isTTY#

Added in: v0.5.8

A `boolean` that is always `true`.

### 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}`);
    });

### 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.isTTY#

Added in: v0.5.8

A `boolean` that is always `true`.

### 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 it is not, including whenever `fd` is not a non-negative integer.