src/vs/code/node/cli.ts/main
export async function main(argv: string[]): Promise<any> {
	let args: NativeParsedArgs;

	try {
		args = parseCLIProcessArgv(argv);
	} catch (err) {
		console.error(err.message);
		return;
	}

	// Help
	if (args.help) {
		const executable = `${product.applicationName}${isWindows ? '.exe' : ''}`;
		console.log(buildHelpMessage(product.nameLong, executable, product.version, OPTIONS));
	}

	// Version Info
	else if (args.version) {
		console.log(buildVersionMessage(product.version, product.commit));
	}

	// Extensions Management
	else if (shouldSpawnCliProcess(args)) {
		const cli = await new Promise<IMainCli>((resolve, reject) => require(['vs/code/node/cliProcessMain'], resolve, reject));
		await cli.main(args);

		return;
	}

	// Write File
	else if (args['file-write']) {
		const source = args._[0];
		const target = args._[1];

		// Validate
		if (
			!source || !target || source === target ||				// make sure source and target are provided and are not the same
			!isAbsolute(source) || !isAbsolute(target) ||			// make sure both source and target are absolute paths
			!existsSync(source) || !statSync(source).isFile() ||	// make sure source exists as file
			!existsSync(target) || !statSync(target).isFile()		// make sure target exists as file
		) {
			throw new Error('Using --file-write with invalid arguments.');
		}

		try {

			// Check for readonly status and chmod if so if we are told so
			let targetMode: number = 0;
			let restoreMode = false;
			if (!!args['file-chmod']) {
				targetMode = statSync(target).mode;
				if (!(targetMode & 0o200 /* File mode indicating writable by owner */)) {
					chmodSync(target, targetMode | 0o200);
					restoreMode = true;
				}
			}

			// Write source to target
			const data = readFileSync(source);
			if (isWindows) {
				// On Windows we use a different strategy of saving the file
				// by first truncating the file and then writing with r+ mode.
				// This helps to save hidden files on Windows
				// (see https://github.com/microsoft/vscode/issues/931) and
				// prevent removing alternate data streams
				// (see https://github.com/microsoft/vscode/issues/6363)
				truncateSync(target, 0);
				writeFileSync(target, data, { flag: 'r+' });
			} else {
				writeFileSync(target, data);
			}

			// Restore previous mode as needed
			if (restoreMode) {
				chmodSync(target, targetMode);
			}
		} catch (error) {
			error.message = `Error using --file-write: ${error.message}`;
			throw error;
		}
	}

	// Just Code
	else {
		const env: IProcessEnvironment = {
			...process.env,
			'ELECTRON_NO_ATTACH_CONSOLE': '1'
		};

		delete env['ELECTRON_RUN_AS_NODE'];

		const processCallbacks: ((child: ChildProcess) => Promise<void>)[] = [];

		const verbose = args.verbose || args.status;
		if (verbose) {
			env['ELECTRON_ENABLE_LOGGING'] = '1';

			processCallbacks.push(async child => {
				child.stdout!.on('data', (data: Buffer) => console.log(data.toString('utf8').trim()));
				child.stderr!.on('data', (data: Buffer) => console.log(data.toString('utf8').trim()));

				await Event.toPromise(Event.fromNodeEventEmitter(child, 'exit'));
			});
		}

		const hasReadStdinArg = args._.some(a => a === '-');
		if (hasReadStdinArg) {
			// remove the "-" argument when we read from stdin
			args._ = args._.filter(a => a !== '-');
			argv = argv.filter(a => a !== '-');
		}

		let stdinFilePath: string | undefined;
		if (hasStdinWithoutTty()) {

			// Read from stdin: we require a single "-" argument to be passed in order to start reading from
			// stdin. We do this because there is no reliable way to find out if data is piped to stdin. Just
			// checking for stdin being connected to a TTY is not enough (https://github.com/microsoft/vscode/issues/40351)

			if (hasReadStdinArg) {
				stdinFilePath = getStdinFilePath();

				// returns a file path where stdin input is written into (write in progress).
				try {
					readFromStdin(stdinFilePath, !!verbose); // throws error if file can not be written

					// Make sure to open tmp file
					addArg(argv, stdinFilePath);

					// Enable --wait to get all data and ignore adding this to history
					addArg(argv, '--wait');
					addArg(argv, '--skip-add-to-recently-opened');
					args.wait = true;

					console.log(`Reading from stdin via: ${stdinFilePath}`);
				} catch (e) {
					console.log(`Failed to create file to read via stdin: ${e.toString()}`);
					stdinFilePath = undefined;
				}
			} else {

				// If the user pipes data via stdin but forgot to add the "-" argument, help by printing a message
				// if we detect that data flows into via stdin after a certain timeout.
				processCallbacks.push(_ => stdinDataListener(1000).then(dataReceived => {
					if (dataReceived) {
						if (isWindows) {
							console.log(`Run with '${product.applicationName} -' to read output from another program (e.g. 'echo Hello World | ${product.applicationName} -').`);
						} else {
							console.log(`Run with '${product.applicationName} -' to read from stdin (e.g. 'ps aux | grep code | ${product.applicationName} -').`);
						}
					}
				}));
			}
		}

		const isMacOSBigSurOrNewer = isMacintosh && release() > '20.0.0';

		// If we are started with --wait create a random temporary file
		// and pass it over to the starting instance. We can use this file
		// to wait for it to be deleted to monitor that the edited file
		// is closed and then exit the waiting process.
		let waitMarkerFilePath: string | undefined;
		if (args.wait) {
			waitMarkerFilePath = createWaitMarkerFile(verbose);
			if (waitMarkerFilePath) {
				addArg(argv, '--waitMarkerFilePath', waitMarkerFilePath);
			}

			// When running with --wait, we want to continue running CLI process
			// until either:
			// - the wait marker file has been deleted (e.g. when closing the editor)
			// - the launched process terminates (e.g. due to a crash)
			processCallbacks.push(async child => {
				let childExitPromise;
				if (isMacOSBigSurOrNewer) {
					// On Big Sur, we resolve the following promise only when the child,
					// i.e. the open command, exited with a signal or error. Otherwise, we
					// wait for the marker file to be deleted or for the child to error.
					childExitPromise = new Promise<void>(resolve => {
						// Only resolve this promise if the child (i.e. open) exited with an error
						child.on('exit', (code, signal) => {
							if (code !== 0 || signal) {
								resolve();
							}
						});
					});
				} else {
					// On other platforms, we listen for exit in case the child exits before the
					// marker file is deleted.
					childExitPromise = Event.toPromise(Event.fromNodeEventEmitter(child, 'exit'));
				}
				try {
					await Promise.race([
						whenDeleted(waitMarkerFilePath!),
						Event.toPromise(Event.fromNodeEventEmitter(child, 'error')),
						childExitPromise
					]);
				} finally {
					if (stdinFilePath) {
						unlinkSync(stdinFilePath); // Make sure to delete the tmp stdin file if we have any
					}
				}
			});
		}

		// If we have been started with `--prof-startup` we need to find free ports to profile
		// the main process, the renderer, and the extension host. We also disable v8 cached data
		// to get better profile traces. Last, we listen on stdout for a signal that tells us to
		// stop profiling.
		if (args['prof-startup']) {
			const portMain = await findFreePort(randomPort(), 10, 3000);
			const portRenderer = await findFreePort(portMain + 1, 10, 3000);
			const portExthost = await findFreePort(portRenderer + 1, 10, 3000);

			// fail the operation when one of the ports couldn't be acquired.
			if (portMain * portRenderer * portExthost === 0) {
				throw new Error('Failed to find free ports for profiler. Make sure to shutdown all instances of the editor first.');
			}

			const filenamePrefix = randomPath(homedir(), 'prof');

			addArg(argv, `--inspect-brk=${portMain}`);
			addArg(argv, `--remote-debugging-port=${portRenderer}`);
			addArg(argv, `--inspect-brk-extensions=${portExthost}`);
			addArg(argv, `--prof-startup-prefix`, filenamePrefix);
			addArg(argv, `--no-cached-data`);

			writeFileSync(filenamePrefix, argv.slice(-6).join('|'));

			processCallbacks.push(async _child => {

				class Profiler {
					static async start(name: string, filenamePrefix: string, opts: { port: number; tries?: number; target?: (targets: Target[]) => Target }) {
						const profiler = await import('v8-inspect-profiler');

						let session: ProfilingSession;
						try {
							session = await profiler.startProfiling(opts);
						} catch (err) {
							console.error(`FAILED to start profiling for '${name}' on port '${opts.port}'`);
						}

						return {
							async stop() {
								if (!session) {
									return;
								}
								let suffix = '';
								const result = await session.stop();
								if (!process.env['VSCODE_DEV']) {
									// when running from a not-development-build we remove
									// absolute filenames because we don't want to reveal anything
									// about users. We also append the `.txt` suffix to make it
									// easier to attach these files to GH issues
									result.profile = Utils.rewriteAbsolutePaths(result.profile, 'piiRemoved');
									suffix = '.txt';
								}

								writeFileSync(`${filenamePrefix}.${name}.cpuprofile${suffix}`, JSON.stringify(result.profile, undefined, 4));
							}
						};
					}
				}

				try {
					// load and start profiler
					const mainProfileRequest = Profiler.start('main', filenamePrefix, { port: portMain });
					const extHostProfileRequest = Profiler.start('extHost', filenamePrefix, { port: portExthost, tries: 300 });
					const rendererProfileRequest = Profiler.start('renderer', filenamePrefix, {
						port: portRenderer,
						tries: 200,
						target: function (targets) {
							return targets.filter(target => {
								if (!target.webSocketDebuggerUrl) {
									return false;
								}
								if (target.type === 'page') {
									return target.url.indexOf('workbench/workbench.html') > 0;
								} else {
									return true;
								}
							})[0];
						}
					});

					const main = await mainProfileRequest;
					const extHost = await extHostProfileRequest;
					const renderer = await rendererProfileRequest;

					// wait for the renderer to delete the
					// marker file
					await whenDeleted(filenamePrefix);

					// stop profiling
					await main.stop();
					await renderer.stop();
					await extHost.stop();

					// re-create the marker file to signal that profiling is done
					writeFileSync(filenamePrefix, '');

				} catch (e) {
					console.error('Failed to profile startup. Make sure to quit Code first.');
				}
			});
		}

		const jsFlags = args['js-flags'];
		if (isString(jsFlags)) {
			const match = /max_old_space_size=(\d+)/g.exec(jsFlags);
			if (match && !args['max-memory']) {
				addArg(argv, `--max-memory=${match[1]}`);
			}
		}

		const options: SpawnOptions = {
			detached: true,
			env
		};

		if (!verbose) {
			options['stdio'] = 'ignore';
		}

		let child: ChildProcess;
		if (!isMacOSBigSurOrNewer) {
			// We spawn process.execPath directly
			child = spawn(process.execPath, argv.slice(2), options);
		} else {
			// On Big Sur, we spawn using the open command to obtain behavior
			// similar to if the app was launched from the dock
			// https://github.com/microsoft/vscode/issues/102975

			// The following args are for the open command itself, rather than for VS Code:
			// -n creates a new instance.
			//    Without -n, the open command re-opens the existing instance as-is.
			// -g starts the new instance in the background.
			//    Later, Electron brings the instance to the foreground.
			//    This way, Mac does not automatically try to foreground the new instance, which causes
			//    focusing issues when the new instance only sends data to a previous instance and then closes.
			const spawnArgs = ['-n', '-g'];
			// -a opens the given application.
			spawnArgs.push('-a', process.execPath); // -a: opens a specific application

			if (verbose) {
				spawnArgs.push('--wait-apps'); // `open --wait-apps`: blocks until the launched app is closed (even if they were already running)

				// The open command only allows for redirecting stderr and stdout to files,
				// so we make it redirect those to temp files, and then use a logger to
				// redirect the file output to the console
				for (const outputType of ['stdout', 'stderr']) {

					// Tmp file to target output to
					const tmpName = randomPath(tmpdir(), `code-${outputType}`);
					writeFileSync(tmpName, '');
					spawnArgs.push(`--${outputType}`, tmpName);

					// Listener to redirect content to stdout/stderr
					processCallbacks.push(async child => {
						try {
							const stream = outputType === 'stdout' ? process.stdout : process.stderr;

							const cts = new CancellationTokenSource();
							child.on('close', () => {
								// We must dispose the token to stop watching,
								// but the watcher might still be reading data.
								setTimeout(() => cts.dispose(true), 200);
							});
							await watchFileContents(tmpName, chunk => stream.write(chunk), () => { /* ignore */ }, cts.token);
						} finally {
							unlinkSync(tmpName);
						}
					});
				}
			}

			for (const e in env) {
				// Ignore the _ env var, because the open command
				// ignores it anyway.
				// Pass the rest of the env vars in to fix
				// https://github.com/microsoft/vscode/issues/134696.
				if (e !== '_') {
					spawnArgs.push('--env');
					spawnArgs.push(`${e}=${env[e]}`);
				}
			}

			spawnArgs.push('--args', ...argv.slice(2)); // pass on our arguments

			if (env['VSCODE_DEV']) {
				// If we're in development mode, replace the . arg with the
				// vscode source arg. Because the OSS app isn't bundled,
				// it needs the full vscode source arg to launch properly.
				const curdir = '.';
				const launchDirIndex = spawnArgs.indexOf(curdir);
				if (launchDirIndex !== -1) {
					spawnArgs[launchDirIndex] = resolve(curdir);
				}
			}

			// We already passed over the env variables
			// using the --env flags, so we can leave them out here.
			// Also, we don't need to pass env._, which is different from argv._
			child = spawn('open', spawnArgs, { ...options, env: {} });
		}

		return Promise.all(processCallbacks.map(callback => callback(child)));
	}
}