Electron open files in read only mode

how to open a file in the defaults app in read only mode?

my app downloads/caches a list of files (ppt's, pdf's etc.) and stores the checksum of each file. before the user opens the file, i need to make sure, that the file hasn't been changed.

the user shall not be able to edit the file, at least he should only be able to edit a temp copy.

i'm using the shell.openItem() command and download the files via electron-dl lib

thanks for help

via Jan Viehweger