List processes by user
Show every process running as root in user format:
ps -U root -u root u
-U is for real ID and -u is for effective ID.
To show numeric id in the USER column, add n.
List processes by PIDs
Show PID 1 and 2 processes in virtual memory format:
ps -q 1,2 v
Process tree on FreeBSD
-d arranges processes into a tree representing parent and child relationships.
ps aux -d