ps manual on macOS (my emphasis):
Display information about other users' processes as well as your own. This will skip any processes which do not have a controlling terminal, unless the
-x option is also specified.
Applications that are running on macOS without a controlling terminal, such as windowed Finder applications, will not be listed by
ps -a. To list these, use
Or, you may may use the
Display information about other users' processes, including those without controlling terminals.
If you are looking for information about a process with a particular name, consider using
(note that case matters, unless you use
To signal a process with a particular name, use
pkill rather than trying to
grep the output of
See the manuals for
Also, even though this was not part of your question,
pstree has a
-s option to show only the branches of the process tree that contains processes with a particular name.