List all open files ...
| all | lsof |
| specific to a user | lsof -u [username] |
| specific to a process | lsoft -p [pid] |
| specific to a file | lsoft -t [filename] |
| specific to a directory | lsoft +D [dirname] |
| IPv4 | lsof -i 4 |
| IPv6 | lsof -i 6 |
| network files | lsof -i |
| port range | lsof -i :1-1024 |
| udp | lsof -i udp |
| tcp | lsof -i tcp |
| parent pid | lsof -R |