node-termios

Access termios settings from nodejs.

The module exports a Termios class, that encapsulates termios struct data:

Properties

• c_iflag: Integer representing the input mode flags.
• c_oflag: Integer representing the output mode flags.
• c_cflag: Integer representing the control mode flags.
• c_lflag: Integer representing the local mode flags.
• c_cc: Buffer representing the control code settings.

Methods

• constructor(from?: number | ITermios | null)
  Create new Termios object. from can be a valid file descriptor (number), another Termios object (copy constructor) or null (all data zeroed out). Omitting from will try to load default values from ttydefaults.h (not supported by all platforms).
• loadFrom(fd: number): void
  Load termios data from file descriptor fd.
• writeTo(fd: number, action?: number): void
  Write termios data to file descriptor fd. action should be one of native.ACTION (default: native.ACTION.TCSAFLUSH).
• getInputSpeed(): number
  Return input channel baud rate setting as in native.BAUD.
• getOutputSpeed(): number
  Return output channel baud rate setting as in native.BAUD.
• setInputSpeed(speed: number): void
  Set input channel baud rate. speed should be one of the baudrates in native.BAUD.
• setOutputSpeed(speed: number): void
  Set output channel baud rate. speed should be one of the baudrates in native.BAUD.
• setSpeed(speed: number): void
  Set input and output channel baud rate. speed should be one of the baudrates in native.BAUD.
• setraw(): void
  Convenient method to set termios data to raw mode (values taken from Python).
• setcbreak(): void
  Convenient method to set termios data to cbreak mode (values taken from Python).
• setcooked(): void
  Convenient method to set termios data back to cooked mode.

The module further exports known symbols defined by the underlying termios.h (platform dependent) and low level functions under native:

• ALL_SYMBOLS: All known symbols.
• IFLAGS: Input mode symbols.
• OFLAGS: Output mode symbols.
• CFLAGS: Character mode symbols.
• LFLAGS: Local mode symbols.
• CC: Valid symbols defined for control character settings.
• ACTION: Actions defined for tcsetattr.
• FLUSH: Symbols for tcflush.
• FLOW: Symbols for tcflow.
• BAUD: Defined baudrates of the platform.
• EXPLAIN: struct termios member alignments and sizes.

Low level functions

The low level function are direct mappings of the C functions, where fd should be a valid TTY file descriptor and buffer is a nodejs buffer of termios struct size (see native.EXPLAIN.size). Additional enum like arguments are mapped in native (see listing above).

Also see termios manpage for further details.

• isatty(fd: number): boolean
  Test if file descriptor fd is a tty. Might throw if fd is not valid.
• ttyname(fd: number): string
  Return tty file name for fd, or empty string (invalid file descriptor).
• ptsname(fd: number): string
  Return pts file name for file descriptor fd, or empty string (invalid file descriptor). Note that this only works on a master end of a PTY. For slave end use ttyname.
• tcgetattr(fd: number, buffer: Buffer): void
  Load termios data for file descriptor fd in buffer. The given buffer must have a length of native.EXPLAIN.size.
• tcsetattr(fd: number, action: number, buffer: Buffer): void
  Write termios data held in buffer to file descriptor fd. action should be one of termios.ACTION. The given buffer must have a length of native.EXPLAIN.size.
• tcsendbreak(fd: number, duration: number): void
• tcdrain(fd: number): void
• tcflush(fd: number, queue_selector: number): void
• tcflow(fd: number, flowaction: number)
• cfgetispeed(buffer: Buffer): void
• cfgetospeed(buffer: Buffer)
• cfsetispeed(buffer: Buffer, speed: number): void
• cfsetospeed(buffer: Buffer, speed: number): void

Examples

The example demostrates how to switch off/on echoing on STDIN:

const { Termios, native: { LFLAGS } } = require('node-termios');
 
// load termios data from STDIN
var t = new Termios(0);
// disable ECHO (not yet written)
t.c_lflag &= ~LFLAGS.ECHO;
// write back to STDIN
t.writeTo(0);
// now interactive input does not show up anymore
...
 
// switch on again when done
t.c_lflag |= LFLAGS.ECHO;
t.writeTo(0);

A typical usage pattern seen in C is to store the settings, do some needed customizations like entering raw mode and restoring old settings afterwards:

const { Termios } = require('node-termios');
 
// save current settings to restore later on
const initial = new Termios(some_tty_fd);
// create copy and enter raw mode
const altered = new Termios(initial);
altered.setraw();
altered.writeTo(some_tty_fd);
// raw mode, thus every single data event shows up
...
// restore old settings
initial.writeTo(some_tty_fd);

Note that in the interactive nodejs shell the standard file descriptors are already customized by the nodejs env and should not be handled like in the example above, or the terminal might break with the shell expectations.

For a silly yet slightly more advanced example, see example.js.