ExtendScript: run external command synchronously

[Nick5EBA]

Is there a way to synchronooously execute a file (i.e., new File(exePath).execute()), but sychronously await the result/with a callback? I don't really want to activate the whole Node.js thing for the child_process command, as I couldn't get it to work the few times I've tried

[Bruce Bullis]

What sort of external ExtendScript command are you hoping to run, synchronously?

[Nick5EBA]

An executable file - I've got that working, but it saves its output to a file that I want it to read after it's finished.

At the moment, I'm using a while loop to test for the file's existence, sleep for 1000ms, then proceed on existence. This causes the script to lock up if the executed script is ended early (i.e., the process dies before file write).

Therefore it'd be much more preferable for it to wait synchronously until the executable has exited, then check for file existence instead.

Thanks for your prompt response!

[Nick5EBA]

Just to clarify, it is the JSX file running the external executable file - currently run as `new File('some.exe').execute()`

[Bruce Bullis]

Interesting...

What is actually being _done_, by that executing script?

[Nick5EBA]

Unfortunately I can't disclose fully what's going on - it's AI for a prorietary plugin, which outputs a JSON file that's used by the rest of the script.

I've been emulating it by calling a batch script with a timeout of 3 seconds during testing, where I came up with that hackjob solution outlined above, if you'd like a way to reproduce:

``` test.bat

timeout 3

echo [ "test" ] > test.json

```

``` index.jsx

var batPath = 'test.bat';

var jsonPath = 'test.json';

var batFile = new File(batPath );

batFile.execute();

while (!File(jsonFile).exists) {

  $.sleep(1000);

}

var output = JSON.parse(jsonFile);

// Rest of script

```

But if you close the terminal window before the timeout finishes, you'll discover the issue! That while loop, I'm assuming keeps on running, freezing up the script after any more calls to $. So it'd obviously be better to run it synchronously and avoid that while loop, as I can just test for file existence once the external command ends. Is that possible?

[Nick5EBA]

Just found out about `system.callSystem` but I can't seem to get that to work. Is that not something that works with Premiere Pro?

[Bruce Bullis]

There is no such call in PPro's ExtendScript API, but you _can_ fire command lines from the JavaScript layer of your panel.

[Nick5EBA]

That sounds promising! Do you have any example? And does that call run synchronously/using a callback?

[Bruce Bullis]

Example = See the CEP HTML Test Panel. 

https://github.com/Adobe-CEP/CEP-Resources/tree/master/CEP_10.x/Samples/CEP_HTML_Test_Extension-10.0

> And does that call run synchronously/using a callback?

No; it's just a normal command line.