Install

Install the pstree with brew:

$ brew install pstree

Show the help doc:

$ pstree --help
pstree: illegal option -- -
pstree $Revision: 2.39 $ by Fred Hucht (C) 1993-2015
EMail: fred AT thp.uni-due.de

Usage: pstree [-f file] [-g n] [-l n] [-u user] [-U] [-s string] [-p pid] [-w] [pid ...]
   -f file   read input from <file> (- is stdin) instead of running
             "ps -axwwo user,pid,ppid,pgid,command"
   -g n      use graphics chars for tree. n=1: IBM-850, n=2: VT100, n=3: UTF-8
   -l n      print tree to n level deep
   -u user   show only branches containing processes of <user>
   -U        don't show branches containing only root processes
   -s string show only branches containing process with <string> in commandline
   -p pid    show only branches containing process <pid>
   -w        wide output, not truncated to window width
   pid ...   process ids to start from, default is 1 (probably init)

Process group leaders are marked with '='.

Samples

Show the tree with the process name:

$ pstree -s terraform
-+= 00001 root /sbin/launchd
 \-+= 50669 larry /Users/larry/Library/Application Support/JetBrains/Toolbox/apps/IDEA-U/ch-0/213.5744.223/IntelliJ ID
   \-+= 51403 larry /bin/bash --rcfile /Users/larry/Library/Application Support/JetBrains/Toolbox/apps/IDEA-U/ch-0/213
     \-+= 55301 larry terraform apply
       \--- 55302 larry /Users/larry/Software/terraform/terraform apply

Show the tree with the process ID(Both parent and child process):

$ pstree -p 55301
-+= 00001 root /sbin/launchd
 \-+= 50669 larry /Users/larry/Library/Application Support/JetBrains/Toolbox/apps/IDEA-U/ch-0/213.5744.223/IntelliJ ID
   \-+= 51403 larry /bin/bash --rcfile /Users/larry/Library/Application Support/JetBrains/Toolbox/apps/IDEA-U/ch-0/213
     \-+= 55301 larry terraform apply
       \--- 55302 larry /Users/larry/Software/terraform/terraform apply

Show the tree with the process ID(child process):

$ pstree 55301
-+= 55301 larry terraform apply
 \--- 55302 larry /Users/larry/Software/terraform/terraform apply