How do I view the IO priority of a process?

Question

How can I view the IO priority of a process? like to see for example if something has been ionice-ed.

Solution

ionice [-p] <pids/>

For example:

$ ionice -p `pidof X`
none: prio 0

This means X is using the none scheduling class (best effort) with priority 0 (highest priority out of 7). Read more with man ionice.