1# TTY 2 3<!--introduced_in=v0.10.0--> 4 5> Stability: 2 - Stable 6 7<!-- source_link=lib/tty.js --> 8 9The `tty` module provides the `tty.ReadStream` and `tty.WriteStream` classes. 10In most cases, it will not be necessary or possible to use this module directly. 11However, it can be accessed using: 12 13```js 14const tty = require('tty'); 15``` 16 17When Node.js detects that it is being run with a text terminal ("TTY") 18attached, [`process.stdin`][] will, by default, be initialized as an instance of 19`tty.ReadStream` and both [`process.stdout`][] and [`process.stderr`][] will, by 20default be instances of `tty.WriteStream`. The preferred method of determining 21whether Node.js is being run within a TTY context is to check that the value of 22the `process.stdout.isTTY` property is `true`: 23 24```console 25$ node -p -e "Boolean(process.stdout.isTTY)" 26true 27$ node -p -e "Boolean(process.stdout.isTTY)" | cat 28false 29``` 30 31In most cases, there should be little to no reason for an application to 32manually create instances of the `tty.ReadStream` and `tty.WriteStream` 33classes. 34 35## Class: `tty.ReadStream` 36<!-- YAML 37added: v0.5.8 38--> 39 40* Extends: {net.Socket} 41 42Represents the readable side of a TTY. In normal circumstances 43[`process.stdin`][] will be the only `tty.ReadStream` instance in a Node.js 44process and there should be no reason to create additional instances. 45 46### `readStream.isRaw` 47<!-- YAML 48added: v0.7.7 49--> 50 51A `boolean` that is `true` if the TTY is currently configured to operate as a 52raw device. Defaults to `false`. 53 54### `readStream.isTTY` 55<!-- YAML 56added: v0.5.8 57--> 58 59A `boolean` that is always `true` for `tty.ReadStream` instances. 60 61### `readStream.setRawMode(mode)` 62<!-- YAML 63added: v0.7.7 64--> 65 66* `mode` {boolean} If `true`, configures the `tty.ReadStream` to operate as a 67 raw device. If `false`, configures the `tty.ReadStream` to operate in its 68 default mode. The `readStream.isRaw` property will be set to the resulting 69 mode. 70* Returns: {this} The read stream instance. 71 72Allows configuration of `tty.ReadStream` so that it operates as a raw device. 73 74When in raw mode, input is always available character-by-character, not 75including modifiers. Additionally, all special processing of characters by the 76terminal is disabled, including echoing input characters. 77`CTRL`+`C` will no longer cause a `SIGINT` when in this mode. 78 79## Class: `tty.WriteStream` 80<!-- YAML 81added: v0.5.8 82--> 83 84* Extends: {net.Socket} 85 86Represents the writable side of a TTY. In normal circumstances, 87[`process.stdout`][] and [`process.stderr`][] will be the only 88`tty.WriteStream` instances created for a Node.js process and there 89should be no reason to create additional instances. 90 91### Event: `'resize'` 92<!-- YAML 93added: v0.7.7 94--> 95 96The `'resize'` event is emitted whenever either of the `writeStream.columns` 97or `writeStream.rows` properties have changed. No arguments are passed to the 98listener callback when called. 99 100```js 101process.stdout.on('resize', () => { 102 console.log('screen size has changed!'); 103 console.log(`${process.stdout.columns}x${process.stdout.rows}`); 104}); 105``` 106 107### `writeStream.clearLine(dir[, callback])` 108<!-- YAML 109added: v0.7.7 110changes: 111 - version: v12.7.0 112 pr-url: https://github.com/nodejs/node/pull/28721 113 description: The stream's write() callback and return value are exposed. 114--> 115 116* `dir` {number} 117 * `-1`: to the left from cursor 118 * `1`: to the right from cursor 119 * `0`: the entire line 120* `callback` {Function} Invoked once the operation completes. 121* Returns: {boolean} `false` if the stream wishes for the calling code to wait 122 for the `'drain'` event to be emitted before continuing to write additional 123 data; otherwise `true`. 124 125`writeStream.clearLine()` clears the current line of this `WriteStream` in a 126direction identified by `dir`. 127 128### `writeStream.clearScreenDown([callback])` 129<!-- YAML 130added: v0.7.7 131changes: 132 - version: v12.7.0 133 pr-url: https://github.com/nodejs/node/pull/28721 134 description: The stream's write() callback and return value are exposed. 135--> 136 137* `callback` {Function} Invoked once the operation completes. 138* Returns: {boolean} `false` if the stream wishes for the calling code to wait 139 for the `'drain'` event to be emitted before continuing to write additional 140 data; otherwise `true`. 141 142`writeStream.clearScreenDown()` clears this `WriteStream` from the current 143cursor down. 144 145### `writeStream.columns` 146<!-- YAML 147added: v0.7.7 148--> 149 150A `number` specifying the number of columns the TTY currently has. This property 151is updated whenever the `'resize'` event is emitted. 152 153### `writeStream.cursorTo(x[, y][, callback])` 154<!-- YAML 155added: v0.7.7 156changes: 157 - version: v12.7.0 158 pr-url: https://github.com/nodejs/node/pull/28721 159 description: The stream's write() callback and return value are exposed. 160--> 161 162* `x` {number} 163* `y` {number} 164* `callback` {Function} Invoked once the operation completes. 165* Returns: {boolean} `false` if the stream wishes for the calling code to wait 166 for the `'drain'` event to be emitted before continuing to write additional 167 data; otherwise `true`. 168 169`writeStream.cursorTo()` moves this `WriteStream`'s cursor to the specified 170position. 171 172### `writeStream.getColorDepth([env])` 173<!-- YAML 174added: v9.9.0 175--> 176 177* `env` {Object} An object containing the environment variables to check. This 178 enables simulating the usage of a specific terminal. **Default:** 179 `process.env`. 180* Returns: {number} 181 182Returns: 183 184* `1` for 2, 185* `4` for 16, 186* `8` for 256, 187* `24` for 16,777,216 188colors supported. 189 190Use this to determine what colors the terminal supports. Due to the nature of 191colors in terminals it is possible to either have false positives or false 192negatives. It depends on process information and the environment variables that 193may lie about what terminal is used. 194It is possible to pass in an `env` object to simulate the usage of a specific 195terminal. This can be useful to check how specific environment settings behave. 196 197To enforce a specific color support, use one of the below environment settings. 198 199* 2 colors: `FORCE_COLOR = 0` (Disables colors) 200* 16 colors: `FORCE_COLOR = 1` 201* 256 colors: `FORCE_COLOR = 2` 202* 16,777,216 colors: `FORCE_COLOR = 3` 203 204Disabling color support is also possible by using the `NO_COLOR` and 205`NODE_DISABLE_COLORS` environment variables. 206 207### `writeStream.getWindowSize()` 208<!-- YAML 209added: v0.7.7 210--> 211 212* Returns: {number[]} 213 214`writeStream.getWindowSize()` returns the size of the [TTY](tty.html) 215corresponding to this `WriteStream`. The array is of the type 216`[numColumns, numRows]` where `numColumns` and `numRows` represent the number 217of columns and rows in the corresponding [TTY](tty.html). 218 219### `writeStream.hasColors([count][, env])` 220<!-- YAML 221added: v11.13.0 222--> 223 224* `count` {integer} The number of colors that are requested (minimum 2). 225 **Default:** 16. 226* `env` {Object} An object containing the environment variables to check. This 227 enables simulating the usage of a specific terminal. **Default:** 228 `process.env`. 229* Returns: {boolean} 230 231Returns `true` if the `writeStream` supports at least as many colors as provided 232in `count`. Minimum support is 2 (black and white). 233 234This has the same false positives and negatives as described in 235[`writeStream.getColorDepth()`][]. 236 237```js 238process.stdout.hasColors(); 239// Returns true or false depending on if `stdout` supports at least 16 colors. 240process.stdout.hasColors(256); 241// Returns true or false depending on if `stdout` supports at least 256 colors. 242process.stdout.hasColors({ TMUX: '1' }); 243// Returns true. 244process.stdout.hasColors(2 ** 24, { TMUX: '1' }); 245// Returns false (the environment setting pretends to support 2 ** 8 colors). 246``` 247 248### `writeStream.isTTY` 249<!-- YAML 250added: v0.5.8 251--> 252 253A `boolean` that is always `true`. 254 255### `writeStream.moveCursor(dx, dy[, callback])` 256<!-- YAML 257added: v0.7.7 258changes: 259 - version: v12.7.0 260 pr-url: https://github.com/nodejs/node/pull/28721 261 description: The stream's write() callback and return value are exposed. 262--> 263 264* `dx` {number} 265* `dy` {number} 266* `callback` {Function} Invoked once the operation completes. 267* Returns: {boolean} `false` if the stream wishes for the calling code to wait 268 for the `'drain'` event to be emitted before continuing to write additional 269 data; otherwise `true`. 270 271`writeStream.moveCursor()` moves this `WriteStream`'s cursor *relative* to its 272current position. 273 274### `writeStream.rows` 275<!-- YAML 276added: v0.7.7 277--> 278 279A `number` specifying the number of rows the TTY currently has. This property 280is updated whenever the `'resize'` event is emitted. 281 282## `tty.isatty(fd)` 283<!-- YAML 284added: v0.5.8 285--> 286 287* `fd` {number} A numeric file descriptor 288* Returns: {boolean} 289 290The `tty.isatty()` method returns `true` if the given `fd` is associated with 291a TTY and `false` if it is not, including whenever `fd` is not a non-negative 292integer. 293 294[`process.stderr`]: process.html#process_process_stderr 295[`process.stdin`]: process.html#process_process_stdin 296[`process.stdout`]: process.html#process_process_stdout 297[`writeStream.getColorDepth()`]: #tty_writestream_getcolordepth_env 298