getpriority, setpriority - get/set program scheduling prior-
int getpriority(int which, int who));
int setpriority(int which, int who, int prio
The scheduling priority of the process, process group, or
user, as indicated by which and who is obtained with the
getpriority call and set with the setpriority call. Which
is one of PRIO_PROCESS, PRIO_PGRP, or PRIO_USER, and who is
interpreted relative to which (a process identifier for
PRIO_PROCESS, process group identifier for PRIO_PGRP, and a
user ID for PRIO_USER). A zero value of who denotes the
current process, process group, or user. Prio is a value in
the range -20 to 20. The default priority is 0; lower
priorities cause more favorable scheduling.
The getpriority call returns the highest priority (lowest
numerical value) enjoyed by any of the specified processes.
The setpriority call sets the priorities of all of the
specified processes to the specified value. Only the
super-user may lower priorities.
Since getpriority can legitimately return the value -1, it
is necessary to clear the external variable errno prior to
the call, then check it afterwards to determine if a -1 is
an error or a legitimate value. The setpriority call
returns 0 if there is no error, or -1 if there is.
ESRCH No process was located using the which and who
EINVAL Which was not one of PRIO_PROCESS, PRIO_PGRP, or
In addition to the errors indicated above, setpriority will
A process was located, but neither its effective nor
real user ID matched the effective user ID of the
A non super-user attempted to lower a process priority.
SVr4, 4.4BSD (these function calls first appeared in
nice(1), fork(2), renice(8)