Display all running processes in the form of a tree.
pstree [options] [pid]
-a shows command-line arguments.
-c does not compact subtrees.
-l displays long lines.
-n sorts processes by process ID (instead of by name).
-p shows process IDs.
The pstree command shows all of the processes in the form of a tree, which makes it easy to understand the parent-child relationships among the processes.