As pfiles.stp takes the target pid both by $1 and -x (target()), plimits.stp should do the same.
Added support for $1 and -x in plimits.stp in this commit: http://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=161c678d113a347b5a89a12f4f5275c2f82e37ab PR14440: made usage of pfiles.stp and plimit.stp more consistent Added support for plimit.stp to accept a target PID through both -x and $1, just like in pfiles.stp. Also removed the //bin/true hack from pfiles.stp and '#!/usr/bin/env stap' from plimit.stp so that both of them must be run using stap -g.