nice
[±
n] commandChange the execution priority for command, or, if none is given, change priority for the current shell. (See also nice in Chapter 2.) The priority range is -20 to 20, with a default of 4. The range is backwards from what you might expect: -20 gives the highest priority (fastest execution); 20 gives the lowest.
+
nAdd n to the priority value (lower job priority).
-
nSubtract n from the priority value (raise job priority). Privileged users only.