Kinda hard to encode it in /etc/passwd, which separates entries with newlines and fields of an entry with colons.
Of course, you can activate some alternative user database in /etc/nsswitch.conf and then you can have your usernames with newlines in them, but at least half of the tools on your system that process usernames will take that personallyâŠ
If I do ps aux | grep root, then the newline is preserved. So I'm not sure what exactly the problem is. There is a user option for ps, but it does not work with aux, ps --user root . You can ps ax --user root, but I'm not sure if this output is what you want.
Btw if you grep, then I recommend using ^user , so it only matches the beginning of each line (the actual username), as ps aux | \grep ^root (notice the backslash). Do you have an alias for grep? Try \grep instead. The backslash in front of the command will use the actual command and ignore your alias.
Here is a little bonus to have in mind: You can convert newline characters to null, then grep with option null, and at last convert null characters back to newline. Now I don't think its useful in this case, but its good to know; therefore its a bonus information: