Node.js

- About these Docs
- Usage & Example

- Assertion Testing
- Async Hooks
- Buffer
- C++ Addons
- C/C++ Addons - N-API
- Child Processes
- Cluster
- Command Line Options
- Console
- Crypto
- Debugger
- Deprecated APIs
- DNS
- Domain
- ECMAScript Modules
- Errors
- Events
- File System
- Globals
- HTTP
- HTTP/2
- HTTPS
- Inspector
- Internationalization
- Modules
- Net
- OS
- Path
- Performance Hooks
- Process
- Punycode
- Query Strings
- Readline
- REPL
- Stream
- String Decoder
- Timers
- TLS/SSL
- Trace Events
- TTY
- UDP/Datagram
- URL
- Utilities
- V8
- VM
- ZLIB

- GitHub Repo & Issue Tracker
- Mailing List

# 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 with a text terminal ("TTY") attached, `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 manually 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` for `tty.ReadStream` instances.

### 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.

### writeStream.getColorDepth([env])#

Added in: v9.9.0

- `env` <Object> A object containing the environment variables to check. Default: `process.env`.
- Returns: <number>

Returns:

- 1 for 2,
- 4 for 16,
- 8 for 256,
- 24 for 16,777,216 colors supported.

Use this to determine what colors the terminal supports. Due to the nature of colors in terminals it is possible to either have false positives or false negatives. It depends on process information and the environment variables that may lie about what terminal is used. To enforce a specific behavior without relying on `process.env` it is possible to pass in an object with different settings.

Use the `NODE_DISABLE_COLORS` environment variable to enforce this function to always return 1.

## 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.