i'm trying to do a tail of the processes under my system.
What do you mean by this? Do you want to run tail on the output of some of your processes? Or do you want
tail to filter the output of your "ps" command, that gives you a list of processes?
Assuming you mean the latter:
ps -aux just lists some running processes once, not continuously, so you don't need tail's -f option.
Also, I think you have the order of the commands reversed:
displays only the last few lines of ps's output. You can control how many lines you want by adding "-n" (replace n with the number you want) to "tail".
And finally, try to start a new thread when you have a question, rather than hijacking someone else's, which is against the forum policy.