Which command changes the niceness (priority) of a running process?

• A. top
• B. nice
• C. renice
• D. kill

Answer: (C)

Renice is the command you use to change the scheduling priority (niceness) of a process that’s already running. Niceness is a hint to the scheduler about how tolerant a process is of waiting for CPU time: lower values mean higher priority, higher values mean lower priority. The range is typically -20 (highest priority) to 19 (lowest). You specify which process to adjust by pid (and you can also target by user or group). For example, renice -n 10 -p 1234 increases the niceness to 10, making it more likely to yield CPU time; renice -n -5 -p 1234 would decrease the niceness (increase priority) if you have the necessary privileges. Nice is used when starting a new process to set its initial niceness, not to adjust an already running one. Kill changes or sends signals to a process but does not alter niceness, and top is a monitoring tool; the direct way to change a running process’s priority is renice.