WINDOWS:
QIE runs as a service on windows. To start and stop the 64 bit version from a script or command prompt use:
net start QIEService64
net stop QIEService64
To check if the service is running use:
net start | find "QIEService64"
or
sc query "QIEService" | find "RUNNING"
For the 32 bit version use QIEService or check the name in windows services.
NOTE: For this to work from a command prompt first use "Run as Administrator"
Also see this bug regarding stopping the QIE service abruptly:
https://www.qvera.com/kb/index.php/671/service-starting-couldnt-lock-programdata-logs-qielauncher?show=671#q671
MACOS:
To start and stop the QIE service on Mac OS open a terminal window and execute the following commands
startQie
stopQie