also want to add that, to run the test code on Linux, one needs to uncheck the "suoUseSize" under pMCX.StartupOptions. Otherwise, you can see an error message "unknown options '-g'" or '-e' (except type 'echo' as the command), this is due to the automatically appended "-geometry 0x0" parameter.
on the Mac, nothing was printed - the TAsyncProcess.onReadData is never fired. If there is something wrong, I would at least expect to see error messages, but none was printed (the TAsyncProcess.Options.poStderrToOutPut is enabled in the component, actually, error messages are printed on Linux).