renice doesn't work in macOS Sierra

Question

I wanted set low priority to HandBrake in macOS.

I tried to use renice command by pid, but it seems not working. (nice value stays 0)

% ps ax -l | grep Hand
  501 32255     1   0  46  0  3433240 544536 -      R      ??   52:50.69 /Applications/HandBrake.app/Contents/MacOS/HandBrake
% sudo renice -p 32255 -n 10
% ps ax -l | grep Hand
  501 32255     1   0  46  0  3433240 530868 -      R      ??   55:58.62 /Applications/HandBrake.app/Contents/MacOS/HandBrake
% sudo renice -p 32255
% ps ax -l | grep Hand
  501 32255     1   0  46  0  3433184 520424 -      R      ??   62:01.50 /Applications/HandBrake.app/Contents/MacOS/HandBrake

It works by using nice like this.

% nice /Applications/HandBrake.app/Contents/MacOS/HandBrake
% ps ax -l | grep Hand
501 32467 30511   0  46 10  2726256 156284 -      SN+  s004    0:00.67 /Applications/HandBrake.app/Contents/MacOS/HandBrake

Am I doing something wrong?

Answer 1

Looking at the man page:

SYNOPSIS

renice priority [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]
renice -n increment [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]

It looks like -n and argument should come before -p.
So try:

sudo renice -n 10 -p 32255

Certainly this is the way I do it on macOS Sierra.