# ionice > Get or set program I/O scheduling class and priority. > Scheduling classes: 1 (realtime), 2 (best-effort), 3 (idle). > Priority levels: 0 (the highest) - 7 (the lowest). > More information: . - Set I/O scheduling class of a running process: `ionice -c {{scheduling_class}} -p {{pid}}` - Run a command with custom I/O scheduling class and priority: `ionice -c {{scheduling_class}} -n {{priority}} {{command}}` - Print the I/O scheduling class and priority of a running process: `ionice -p {{pid}}`