Say you are using netstat to checl all established network connections on a windows machine (confirmed to work on windows 7+ and windows server 2008+) and want to find out how many connections you have, you can use
netstat -an | find "ESTABLISHED" | find /v /c ""
breaking down the command string
netstat -an : Uses netstat command to display all connections and listening ports (-a) and displays them in numerical form instead of resolving DNS or using common names (-n)
| : piping (passing) output of one command to the next one
find “ESTABLISHED” : Uses find command to filter out to just lines that contain the string “ESTABLISHED”‘
find /c /v “” : exclude blank lines (/v “”) and count the number of remaining lines (/c)
If you wanted to something similar in linux, you can use
netstat -an | grep "ESTABLISHED" | wc -l