BigSurBug: helper apps won't launch reliably from shell

Targets macOS
1

I have a main app which launches one or more copies of helper apps stored in the .app/Contents/Helpers/ folder. The apps are launched with the following code:

Window1.helpers() as Shell  

 Window1.LaunchHelpers
 const numberHelperApps = 8
  for i as integer = 1 to numberHelperApps
    dim cmd as string = "env FLAGS=-foobar" + str(i)  + " open -gn " +  appFile.shellPath
    dim sh as new shell 
    sh.mode = 1 
    sh.Execute cmd
    helpers.append sh // keep a reference so the shell never goes out of scope and gets destroyed
 next

This has worked well for years across multiple macOS versions. Suddently, in Big Sur, it’s inconsistent - sometimes I get 8 helpers launched, sometimes 7, 6, 4 or even just one.

However, if I run the equivalent command in Terminal:

for i in {1..8}; do echo $i; open -gn MyApp.app/Contents/Helpers/MyHelper.app ; done

I always get 8 apps launched.

Any ideas why?

2

If you run a test script from the shell that logs to a file do you always get 8 runs?

3

On further investigation

  • my actual code is using the & operator in the shell commend, e.g.
    open -gn MyApp.app/Contents/Helpers/MyHelper.app &
  • and I’m also using mode 1 (asynchronous) shells.

So my theory is that perhaps in Big Sur, the command open -gn if run quickly enough, is not detecting the very first launch of the app (the “-n” option means “open a new instance even if it’s running”. The “&” in the shell command means “run this command in the background, don’t wait for it to finish”

Setting the Shell to mode 0 (synchronous) and removing the background “&” from the command seems to fix the problem, at some cost in slower launch time for the main app.

4

Dont you need a “;” after the env and before the open?

5

You might think so, but actually the “env” command takes parameters followed by the next command, so
env foo=bar echo "hello"
is valid BASH

6

I know it’s valid, but i suspect it might have something to do with how mac allows the “open” command to be used.

7

Possible, but whatever it is worked fine for over 10 years until Big Sur…

8

Add that to the growing list.