TTY#

Stability: 2 - Stable

Source Code: lib/tty.js

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#

Added in: v0.5.8

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.

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#

Added in: v0.5.8

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

readStream.setRawMode(mode)#

Added in: v0.7.7
  • 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.
  • 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. Ctrl+C 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.

Class: tty.WriteStream#

Added in: v0.5.8

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])#

History
VersionChanges
v0.9.4

The options argument is supported.

v0.5.8

Added in: v0.5.8

Creates a ReadStream for fd associated with a TTY.

new tty.WriteStream(fd)#

Added in: v0.5.8

Creates a WriteStream for fd associated with a TTY.

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.clearLine(dir[, callback])#

History
VersionChanges
v12.7.0

The stream's write() callback and return value are exposed.

v0.7.7

Added in: v0.7.7

  • 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])#

History
VersionChanges
v12.7.0

The stream's write() callback and return value are exposed.

v0.7.7

Added in: v0.7.7

  • 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#

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