repl.start()

repl.start([options])

Returns and starts a REPLServer instance, that inherits from Readline Interface. Accepts an "options" Object that takes the following values:

• prompt - the prompt and stream for all I/O. Defaults to > .

• input - the readable stream to listen to. Defaults to process.stdin.

• output - the writable stream to write readline data to. Defaults to process.stdout.

• terminal - pass true if the stream should be treated like a TTY, and have ANSI/VT100 escape codes written to it. Defaults to checking isTTY on the output stream upon instantiation.

• eval - function that will be used to eval each given line. Defaults to an async wrapper for eval(). See below for an example of a custom eval.

• useColors - a boolean which specifies whether or not the writer function should output colors. If a different writer function is set then this does nothing. Defaults to the repl's terminal value.

• useGlobal - if set to true, then the repl will use the global object, instead of running scripts in a separate context. Defaults to false.

• ignoreUndefined - if set to true, then the repl will not output the return value of command if it's undefined. Defaults to false.

• writer - the function to invoke for each command that gets evaluated which returns the formatting (including coloring) to display. Defaults to util.inspect.

• replMode - controls whether the repl runs all commands in strict mode, default mode, or a hybrid mode ("magic" mode.) Acceptable values are:

  • repl.REPL_MODE_SLOPPY - run commands in sloppy mode.
  • repl.REPL_MODE_STRICT - run commands in strict mode. This is equivalent to prefacing every repl statement with 'use strict'.
  • repl.REPL_MODE_MAGIC - attempt to run commands in default mode. If they fail to parse, re-try in strict mode.

You can use your own eval function if it has following signature:

function eval(cmd, context, filename, callback) {
  callback(null, result);
}

On tab completion, eval will be called with .scope as an input string. It is expected to return an array of scope names to be used for the auto-completion.

Multiple REPLs may be started against the same running instance of Node.js. Each will share the same global object but will have unique I/O.

Here is an example that starts a REPL on stdin, a Unix socket, and a TCP socket:

const net = require('net');
const repl = require('repl');
var connections = 0;

repl.start({
  prompt: 'Node.js via stdin> ',
  input: process.stdin,
  output: process.stdout
});

net.createServer((socket) => {
  connections += 1;
  repl.start({
    prompt: 'Node.js via Unix socket> ',
    input: socket,
    output: socket
  }).on('exit', () => {
    socket.end();
  })
}).listen('/tmp/node-repl-sock');

net.createServer((socket) => {
  connections += 1;
  repl.start({
    prompt: 'Node.js via TCP socket> ',
    input: socket,
    output: socket
  }).on('exit', () => {
    socket.end();
  });
}).listen(5001);

Running this program from the command line will start a REPL on stdin. Other REPL clients may connect through the Unix socket or TCP socket. telnet is useful for connecting to TCP sockets, and socat can be used to connect to both Unix and TCP sockets.

By starting a REPL from a Unix socket-based server instead of stdin, you can connect to a long-running Node.js process without restarting it.

For an example of running a "full-featured" (terminal) REPL over a net.Server and net.Socket instance, see: https://gist.github.com/2209310

For an example of running a REPL instance over curl(1), see: https://gist.github.com/2053342