Linux Shells by Example

pstree—displays a tree of processes

pstree [-a] [-c] [-h] [-l] [-n] [-p] [-u] [-G|-U][pid|user]
pstree -V

pstree shows running processes as a tree. The tree is rooted at either pid or init if pid is omitted. If a username is specified, all process trees rooted at processes owned by that user are shown. pstree visually merges identical branches by putting them in square brackets and prefixing them with the repetition count, for example:

            init-+-getty
                |-getty
                |-getty
                '-getty

becomes

          init---4*[getty]