how does quarantine works in clamAV?

You said Clam AV, but I suppose you mean ClamWin, which is the topic of these forums. ClamWin does use the scan engine and signature database of Clam AV, so I suppose that quarantine is the same process in both AVs. When the scan engine finds a signature from its signature database in a file, ClamWin moves the file to its quarantine folder and inserts an "infected" at the end of the filename so the file can not be executed. If you want to know more, lI suggest that you inspect the ClamWin source code--it is open source. If you use the source code, you must abide by the open source requirements, and I suggest that you read up on the requirements.

Regards,