From a shell running at the default nice value of 0, which command starts `./render.sh` with nice value 15 so it competes weakly for CPU time?
LPIC-1 Exam 101-500, objective 103. GNU and Unix commands medium
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The options
Not correct renice -n 15 ./render.sh
Wrong tool. renice changes an already running process and expects a PID, a user or a process group — not a command to start.
Correct nice -n 15 ./render.sh
Correct. nice launches a new command after adding the given adjustment to the shell's own nice value, so from the usual nice 0 the job runs at 15 and yields CPU to everything more important.
Not correct nice -n -15 ./render.sh
Wrong sign. A negative nice value raises priority, which is the opposite of what was asked, and it would additionally require root.
Not correct nice -p 15 ./render.sh
Wrong. nice has no -p option; -p for selecting a PID belongs to renice. GNU nice rejects it with 'invalid option -- p' and exits without running anything.
Why
nice starts a new process with an adjusted nice value; renice changes one that already exists. The number after -n is an increment added to the shell's current nice value, which is 0 in a normal login shell, so `nice -n 15` gives 15. Remember that `nice cmd` with no -n adds 10 (GNU coreutils) rather than setting the value to 0.
Where this comes from
- Cited
- LPI exam objective 103.6
- What it says
- Start a program with a chosen scheduling priority using nice.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 103 and space the ones you get wrong.