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The
scheduling priority of the process, process group, or user, as indicated
by and is obtained with the call and set with the call. is one of
or and is interpreted relative to (a process identifier for process
group identifier for and a user ID for A zero value of denotes the current
process, process group, or user. is a value in the range -20 to 20. The
default priority is 0; lower priorities cause more favorable scheduling.
The call returns the highest priority (lowest numerical value) enjoyed
by any of the specified processes. The call sets the priorities of all
of the specified processes to the specified value. Only the super-user may
lower priorities.
Since can legitimately return the value
-1, it is necessary to clear the external variable prior to the call, then
check it afterward to determine if a -1 is an error or a legitimate value.
The call returns 0 if there is no error, or -1 if there is.
and
will fail if: No process was located using the and values specified.
was not one of or In addition to the errors indicated above, will
fail if: A process was located, but neither its effective nor real user
ID matched the effective user ID of the caller. A non super-user attempted
to lower a process priority.
The function call appeared
in
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