tty
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:
import tty from '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.
Usage in Deno
import * as mod from "node:tty";
Classes
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.
Represents the writable side of a TTY. In normal circumstances, process.stdout and process.stderr will be the onlytty.WriteStream instances created for a Node.js process and there
should be no reason to create additional instances.
Functions
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.
Type Aliases
class ReadStream
Usage in Deno
import { ReadStream } from "node:tty";
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.
Constructors #
#ReadStream(fd: number,options?: net.SocketConstructorOpts,) Properties #
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.
Methods #
#setRawMode(mode: boolean): this 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. Ctrl+C will no longer cause a SIGINT when
in this mode.
class WriteStream
Usage in Deno
import { WriteStream } from "node:tty";
Represents the writable side of a TTY. In normal circumstances, process.stdout and process.stderr will be the onlytty.WriteStream instances created for a Node.js process and there
should be no reason to create additional instances.
Constructors #
#WriteStream(fd: number) Properties #
A number specifying the number of columns the TTY currently has. This property
is updated whenever the 'resize' event is emitted.
Methods #
#addListener(event: string,listener: (...args: any[]) => void,): this #addListener(event: "resize",listener: () => void,): this writeStream.clearLine() clears the current line of this WriteStream in a
direction identified by dir.
#clearScreenDown(callback?: () => void): boolean writeStream.clearScreenDown() clears this WriteStream from the current
cursor down.
writeStream.cursorTo() moves this WriteStream's cursor to the specified
position.
#getColorDepth(env?: object): number Returns:
1for 2,4for 16,8for 256,24for 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.
#getWindowSize(): [number, 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.
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).
#moveCursor(dx: number,dy: number,callback?: () => void,): boolean writeStream.moveCursor() moves this WriteStream's cursor relative to its
current position.
#prependListener(event: string,listener: (...args: any[]) => void,): this #prependListener(event: "resize",listener: () => void,): this #prependOnceListener(event: string,listener: (...args: any[]) => void,): this #prependOnceListener(event: "resize",listener: () => void,): this function isatty
Usage in Deno
import { isatty } from "node:tty";