TTY

Stability: 2 - Stable

The node: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('node: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`

Extends: {net.Socket}

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`

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

This flag is always false when a process starts, even if the terminal is operating in raw mode. Its value will change with subsequent calls to setRawMode.

`readStream.isTTY`

A boolean that is always true for tty.ReadStream instances.

`readStream.setRawMode(mode)`

mode {boolean|string} If true or 'raw', configures the tty.ReadStream to operate as a raw device. If 'io', configures the tty.ReadStream to operate in binary-safe I/O mode. If false, configures the tty.ReadStream to operate in its default mode. The readStream.isRaw property will be set to whether the stream is in raw mode, and the readStream.rawMode property will be set to the resulting mode.
Returns: {this} The read stream instance.

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 input characters by the terminal is disabled, including echoing input characters. <kbd>Ctrl</kbd>+<kbd>C</kbd> will no longer cause a SIGINT when in this mode. This mode does not affect terminal output processing, such as newline translation on Unix terminals.

On Windows, setRawMode() requires write permission to the console input buffer. When opening “\\\\.\\CONIN$” with the [fs.open()][] family of APIs (for passing into new tty.ReadStream()), be sure to use a read/write flag such as 'r+'.

When in binary-safe I/O mode, terminal output processing is also disabled. This corresponds to libuv's UV_TTY_MODE_IO mode and is not supported on Windows.

`readStream.rawMode`

{boolean|string}

The current raw mode for the tty.ReadStream. This is false when the stream is in its default mode, 'raw' when raw input mode is enabled, and 'io' when binary-safe I/O mode is enabled.

Class: `tty.WriteStream`

Extends: {net.Socket}

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.

`new tty.ReadStream(fd[, options])`

fd {number} A file descriptor associated with a TTY.
options {Object} Options passed to parent net.Socket, see options of [net.Socket constructor][].
Returns: {tty.ReadStream}

Creates a ReadStream for fd associated with a TTY.

`new tty.WriteStream(fd)`

fd {number} A file descriptor associated with a TTY.
Returns: {tty.WriteStream}

Creates a WriteStream for fd associated with a TTY.

Event: `'resize'`

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.clearLine(dir[, callback])`

dir {number}
-1: to the left from cursor
1: to the right from cursor
0: the entire line
callback {Function} Invoked once the operation completes.
Returns: {boolean} false if the stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

writeStream.clearLine() clears the current line of this WriteStream in a direction identified by dir.

`writeStream.clearScreenDown([callback])`

callback {Function} Invoked once the operation completes.
Returns: {boolean} false if the stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

writeStream.clearScreenDown() clears this WriteStream from the current cursor down.

`writeStream.columns`

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

`writeStream.cursorTo(x[, y][, callback])`

x {number}
y {number}
callback {Function} Invoked once the operation completes.
Returns: {boolean} false if the stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

writeStream.cursorTo() moves this WriteStream's cursor to the specified position.

`writeStream.getColorDepth([env])`

env {Object} An object containing the environment variables to check. This enables simulating the usage of a specific terminal. 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. It is possible to pass in an env object to simulate the usage of a specific terminal. This can be useful to check how specific environment settings behave.

To enforce a specific color support, use one of the below environment settings.

2 colors: FORCE_COLOR = 0 (Disables colors)
16 colors: FORCE_COLOR = 1
256 colors: FORCE_COLOR = 2
16,777,216 colors: FORCE_COLOR = 3

Disabling color support is also possible by using the NO_COLOR and NODE_DISABLE_COLORS environment variables.

`writeStream.getWindowSize()`

Returns: {number[]}

writeStream.getWindowSize() returns the size of the TTY corresponding to this WriteStream. The array is of the type [numColumns, numRows] where numColumns and numRows represent the number of columns and rows in the corresponding TTY.

`writeStream.hasColors([count][, env])`

count {integer} The number of colors that are requested (minimum 2). Default: 16.
env {Object} An object containing the environment variables to check. This enables simulating the usage of a specific terminal. Default: process.env.
Returns: {boolean}

Returns true if the writeStream supports at least as many colors as provided in count. Minimum support is 2 (black and white).

This has the same false positives and negatives as described in [writeStream.getColorDepth()][].

process.stdout.hasColors();
// Returns true or false depending on if `stdout` supports at least 16 colors.
process.stdout.hasColors(256);
// Returns true or false depending on if `stdout` supports at least 256 colors.
process.stdout.hasColors({ TMUX: '1' });
// Returns true.
process.stdout.hasColors(2 ** 24, { TMUX: '1' });
// Returns false (the environment setting pretends to support 2 ** 8 colors).

`writeStream.isTTY`

A boolean that is always true.

`writeStream.moveCursor(dx, dy[, callback])`

dx {number}
dy {number}
callback {Function} Invoked once the operation completes.
Returns: {boolean} false if the stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

writeStream.moveCursor() moves this WriteStream's cursor relative to its current position.

`writeStream.rows`

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

`tty.isatty(fd)`

fd {number} A numeric file descriptor
Returns: {boolean}

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.

TTY

TTY

Class: tty.ReadStream

readStream.isRaw

readStream.isTTY

readStream.setRawMode(mode)

readStream.rawMode

Class: tty.WriteStream

new tty.ReadStream(fd[, options])

new tty.WriteStream(fd)

Event: 'resize'

writeStream.clearLine(dir[, callback])

writeStream.clearScreenDown([callback])

writeStream.columns

writeStream.cursorTo(x[, y][, callback])

writeStream.getColorDepth([env])

writeStream.getWindowSize()

writeStream.hasColors([count][, env])

writeStream.isTTY

writeStream.moveCursor(dx, dy[, callback])

writeStream.rows

tty.isatty(fd)

Class: `tty.ReadStream`

`readStream.isRaw`

`readStream.isTTY`

`readStream.setRawMode(mode)`

`readStream.rawMode`

Class: `tty.WriteStream`

`new tty.ReadStream(fd[, options])`

`new tty.WriteStream(fd)`

Event: `'resize'`

`writeStream.clearLine(dir[, callback])`

`writeStream.clearScreenDown([callback])`

`writeStream.columns`

`writeStream.cursorTo(x[, y][, callback])`

`writeStream.getColorDepth([env])`

`writeStream.getWindowSize()`

`writeStream.hasColors([count][, env])`

`writeStream.isTTY`

`writeStream.moveCursor(dx, dy[, callback])`

`writeStream.rows`

`tty.isatty(fd)`