@ Yann58
Try ashquick.exe as that was used for some browser settings to request that a downloaded file was scanned. However that is/was pretty redundant as the Web Shield and File System Shield would have scanned.
* Note it isn't the regular Avast Service/executable for the on-access antivirus scanner.
So I'm not sure of the purpose you are intending to use it as you couldn't launch the regular Avast Service/executable as it isn't designed as a command line scanner.