How to correctly execute the cd command from inside of Node.js?

Question

I'm developing a very simple Electron app for Windows which, when executed from the command prompt, opens a dialog box trough which the user can select a folder. The app would then change the command prompt directory to the directory selected by the user.

My end goal is to be able to simply type dirnav, select a folder from the dialog box and have the app take care of redirecting the command prompt to the selected directory (instead of typing cd C:\Users\myName\whateverDirectory. Here's what I have so far:

const exec     = require('child_process').exec;
const electron = require('electron');
const {app, dialog} = electron;

app.on('ready', () => {
    dialog.showOpenDialog(
        {
            title: 'Select a directory',
            defaultPath: '.',
            buttonLabel: 'Select',
            properties: ['openDirectory']
        }, (responce) => {
            exec('cd ' + responce[0], () => {
                app.quit();
            });
        }
    );
});

Unfortunately, simply doing exec('cd ' + responce[0]) doesn't seem to work, because instead of changing the directory of the command prompt the application was runned from, it changes the directory of another (unknown to me) command prompt. Is there any way to work around that?

It is unclear what process you are trying to change the directory for. When you run exec() it makes a new command prompt that has it's entirely own environment. As you have discovered, changing the directory in that and then letting that shell window exit just changes the current directory in that shell prompt and does not affect anything else. — jfriend00
– jfriend00, Commented Jul 8, 2018 at 1:39
You will need to tell us what real problem you're trying to solve? Perhaps you should just remember the path they select in your app and use that as the defaultPath for future operations yourself? — jfriend00
– jfriend00, Commented Jul 8, 2018 at 1:40
There's no cd.exe, try running where cd and see. That's because a process can only change it's environment, and the changes will be lost when it exits. Therefore cd has to be an internal command. Same in *nix — phuclv
– phuclv, Commented Jul 8, 2018 at 1:49
There is no such thing as cd.exe. cd is an internal command of cmd.exe, just as dir, cls and echo are internal to cmd.exe.. In addition, cd only affects the currently open command (terminal) window, and what your code is doing doesn't make much sense calling cd. — Ken White
– Ken White, Commented Jul 8, 2018 at 1:55
OK, it would help if you "edit" your question to explain that that is the end goal of what you're trying to do. I'm guessing that maybe you can launch your app with a batch file, have your electron app write something to stdout that can be used by the batch file to change the current directory in the shell in which the batch file is running. But, I don't know exactly how to do that. — jfriend00
– jfriend00, Commented Jul 8, 2018 at 16:09

jfriend00 · Accepted Answer · 2018-07-09 06:57:20Z

1

Here's a simple scheme that will work from a batch file:

for /f %%i in ('node yourapp.js') do set NEWDIR=%%i
cd %NEWDIR%

And, my yourapp.js is this (just to prove that the concept works):

process.stdout.write("subdir");

This will end up executing in the batch file:

cd subdir

You should be able to plug in your electron showOpenDialog() in your own app and then just write the result to process.stdout.

The for loop in the batch file does indeed look odd, but it's the only way I found that people have found to get the stdout from an app into an environment variable that you can then use later in the batch file. You could, of course also use a temp file (redirect output to a temp file), but I thought an environment variable was a cleaner solution.

edited Jul 9, 2018 at 6:57

answered Jul 9, 2018 at 4:50

jfriend00

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