cameron$ echo “fib=lambda n: (n in (0,1) and [n] or [fib(n-1)+fib(n-2)])[0];print fib(38)” | python &
[1] 76611
cameron$ ps -o command,pid,pri,ni -p 76611
COMMAND PID PRI NI
python 76611 31 0
cameron$ sudo renice -4 76611
cameron$ ps -o command,pid,pri,ni -p 76611
COMMAND PID PRI NI
python 76611 35 -4
cameron$ sudo renice -5 76611
cameron$ ps -o command,pid,pri,ni -p 76611
COMMAND PID PRI NI
python 76611 36 -5

so, it looks like the command sets the nice value to the given value, rather than moving it relative to what is was before.

Great question. I too am still confused by the usage of this command. This also seems quite strange to me…

“User cannot lower the nice values of their processes after they’ve raised them.” Why would that be?

That’s not really correct. It is possible for users to go down to nice value 0, e.g. by not using the nice command when starting processes. This results in processes having *priority* 20. Prority and nice-values belong together (NI 0 => PR 20, NI 19 => PR 39, NI -20 => PR 0).

According to the manual, renice can use delta values like +3 or -2 for changing nice values, but to me it seems unclear what happens when entering “renice -5 ” as root – does that mean a nice value of -5 or lowering the existing nice value by 5?