setpriority

setpriority 
which
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who
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priority

Sets the current priority for a process, a process group, or a user. which must indicate one of these types: PRIO_PROCESS , PRIO_PGRP , or PRIO_USER . who therefore identifies the specific process, process group, or user with its ID. priority is an integer number that will be added to or subtracted from the current priority; the lower the number, the higher the priority. The interpretation of a given priority may vary from one operating system to the next. See setpriority on your system. Invoking setpriority will produce a fatal error if used on a machine that doesn't implement setpriority .