To scan a file you have to download it. You can only scan it on the server if it is your server and you have remote access to it. So if you want to download it from the terminal and run a scan as soon as it is downloaded, you should use a command like:
wget -O /tmp/filetoscan http://LINK_TO_THE_FILE && clamscan /tmp/filetoscan
or if you don't need the file after download, you can pipe it to clamscan:
wget -qO- http://LINK_TO_THE_FILE | clamscan -
The above will still download the file, the only difference is that it won't store it on your storage. (So your bandwith will be still used during the process, and if you decide that the file is clean, you have to redownload it if you need it on your pc.)
If you don't want to download it, then you have to use a cloud service which downloads and scans it for you, e.g virustotal does it and it scans the file with ClamAV also. Virustotal also has a public API which you can use to initiate scans from your terminal or from any program you write.
If it is your server with clamAV installed on it and you have ssh access to it, then you just ssh to the server and scan the file just like you would scan it on your client. You can use somwthing like:
ssh YOUR_USER@`echo "example.com/file1" | awk -F "/" '{print $1}'` "clamscan /var/www`echo "example.com/file1" | awk -F ".com" '{print $2}'`"
Of course this depends on your server root (/var/www) and whether there are other settings on the server which should be taken into an account when reconstructing the filepath from the URL, but because you know how your server is set up you can do it.
Although rare, Linux malware & viruses do exist. The strict layered structure of Linux makes it however less vulnarable, but not immune. It can also not be excluded that you make a mistake, and authorize a malicious piece of software to do harmfull things.
In practice however, you will mainly use a virusscanner to protect your Windows partners. ClamAV does scan for Windows viruses as well.
Best Answer
1. Yes, it does, and by default as you can see from
man clamscan, it is turned on (the*indicates the default option):2. The more important question you should be asking is "Does ClamAV scan for viruses that affect Linux as well?", because the majority of viruses ClamAV detects are Windows viruses.