No, "-axuf" is a weird mixture of BSD and POSIX syntax. From the ps manpage: Note that "ps -aux" is distinct from "ps aux". The POSIX and UNIX standards requ

No, "-axuf" is a weird mixture of BSD and POSIX syntax. From the ps manpage: Note that "ps -aux" is distinct from "ps aux". The POSIX and UNIX standards require that "ps -aux" print all processes owned by a user named "x", as well as printing all processes that would be selected by the -a option. If the user named "x" does not exist, this ps may interpret the command as "ps aux" instead and print a warning. This behavior is intended to aid in transitioning old scripts and habits. It is fragile, subject to change, and thus should not be relied upon.