The commands in their example are not equivalent. The ps | grep thing searches the full command line including argument while ps -C (and, presumably, the psc thing) just returns the process name.

Should you for some reason want to do the former, this is easiest done using:

  pgrep -u root -f nginx

which exists on almost all platforms, with the notable exception of AIX.

Their other slightly convoluted example is:

  psc 'socket.state == established && socket.dstPort == uint(443)'

which is much more succinct with:

  lsof -i :443 -s TCP:ESTABLISHED