network bash lsof - ghdrako/doc_snipets GitHub Wiki
lsof - lists open files (kernel-level functionality), but it's also capable of determining which processes are using those opened files. Keep in mind that, in Unix operating systems, almost everything is a file, which also includes objects such as network sockets. As such, lsof is often used when dealing with security aspects of our Linux systems, as it obviously gives many more technical details when compared to netstat.
Show process that use internet connection at the moment
lsof -P -i -n
Show process that use specific port number
lsof -i tcp:443
Lists all listening ports together with the PID of the associated process
lsof -Pan -i tcp -i udp
List all open ports and their owning executables
lsof -i -P | grep -i "listen"
Show all open ports
lsof -Pnl -i
Show open ports (LISTEN)
lsof -Pni4 | grep LISTEN | column -t
List all files opened by a particular command
lsof -c "process"
View user activity per directory
lsof -u username -a +D /etc
Show 10 largest open files
lsof / | \
awk '{ if($7 > 1048576) print $7/1048576 "MB" " " $9 " " $1 }' | \
sort -n -u | tail | column -t
Show current working directory of a process
lsof -p <PID> | grep cwd