Why is __dirname not defined in node REPL?

From the node manual I see that I can get the directory of a file with __dirname, but from the REPL this seems to be undefined. Is this a misunderstanding on my side or where is the error?

$ node
> console.log(__dirname)
ReferenceError: __dirname is not defined
    at repl:1:14
    at REPLServer.eval (repl.js:80:21)
    at Interface.<anonymous> (repl.js:182:12)
    at Interface.emit (events.js:67:17)
    at Interface._onLine (readline.js:162:10)
    at Interface._line (readline.js:426:8)
    at Interface._ttyWrite (readline.js:603:14)
    at ReadStream.<anonymous> (readline.js:82:12)
    at ReadStream.emit (events.js:88:20)
    at ReadStream._emitKey (tty.js:320:10)

__dirname is only defined in scripts. It's not available in REPL.

try make a script a.js

console.log(__dirname);

and run it:

node a.js

you will see __dirname printed.

Added background explanation: __dirname means 'The directory of this script'. In REPL, you don't have a script. Hence, __dirname would not have any real meaning.

Building on the existing answers here, you could define this in your REPL:

__dirname = path.resolve(path.dirname(''));

Or:

__dirname = path.resolve();

If no path segments are passed, path.resolve() will return the absolute path of the current working directory.

Or @Jthorpe's alternatives:

__dirname = process.cwd();
__dirname = fs.realpathSync('.');
__dirname = process.env.PWD

If you are using Node.js modules, __dirname and __filename don't exist.

From the Node.js documentation:

No require, exports, module.exports, __filename, __dirname

These CommonJS variables are not available in ES modules.

require can be imported into an ES module using module.createRequire().

Equivalents of __filename and __dirname can be created inside of each file via import.meta.url:

import { fileURLToPath } from 'url';
import { dirname } from 'path';

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

https://nodejs.org/docs/latest-v15.x/api/esm.html#esm_no_filename_or_dirname

In ES6 use:

import path from 'path';
const __dirname = path.resolve();

also available when node is called with --experimental-modules

As @qiao said, you can't use __dirname in the node repl. However, if you need need this value in the console, you can use path.resolve() or path.dirname(). Although, path.dirname() will just give you a "." so, probably not that helpful. Be sure to require('path').