lsof lists open files on a Linux or Unix system. It is useful because sockets, devices, directories and regular files can all appear as open files.
Find which process is using a port
lsof -i :8080List open files for a process
lsof -p 1234List files opened by a user
lsof -u usernameThis command is helpful when troubleshooting ports, locked files, deleted files still held open by a process, or unexpected file usage.