Question: how to check if you are connected to internet linux?
Answer: Ping Test. The very first tool I use to check if connected to internet is via ping utility. ... 
Check port availability using cat, echo.. There are various tools which can be used to check port availability which I will share in this article. ... 
DNS lookup using nslookup, host etc.. ... 
Curl. ... 
Telnet. ... 
Nmap. ... 
netcat or nc. ... 
wget.