How to scan a folder in command line?

I am trying to get avast 1.3.0-2 i386deb to work on ubuntu 14.04 64bit.
I installed using software center. I could not start avast using the menu icon.
Then I used an advice I found on the forum.
sudo dpkg -i —force-architecture avast4workstation_1.3.0-2_i386.deb
I expect it makes i386 software work on 64bit system.
I set shmmax to 192000000. After reading posts on this forum, I do not know what value to set.
I could not start avast using menu icon. Then sudo avast -a. In command line, I could enter the key.
And sudo avast-update appeared to update avast’s defs.
I cannot get avast gui to start. How can I in command line do a scanning of a folder? What do I write in command line?

Thank you.