lsof command

1. To list all open files, run lsof without any arguments

losf

The same with

lsof -i

2. To list files opened by processes belonging to a specific users

lsof -u [user-name]

3. To list opened files based on their internet address(IPV4 || IPV6)

lsof  -i 4
lsof -i 6

4. List opened files specific to a process

lsof -p [process-id]

To exclude a specific process, can run the following command

lsof -p [^PID]

5. List IDs of processes which open a specific file

lsof -t [file-name]

6. Limit lsof to a specific directory

lsof +D [directory-path]

7. List open files with port range

lsof -i [1-1024]

8. List open files based on connection types

lsof -i udp
lsof -i tcp

9. List parent process opened files

lsof -R

To get a PPID information for s specific PID, you can run the following command

lsof -p 3 -R