1GETPRIORITY(2)                System Calls Manual               GETPRIORITY(2)
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NAME

6       getpriority, setpriority - get/set program scheduling priority
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SYNOPSIS

9       #include <sys/resource.h>
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11       prio = getpriority(which, who)
12       int prio, which, who;
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14       setpriority(which, who, prio)
15       int which, who, prio;
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DESCRIPTION

18       The  scheduling  priority  of  the  process, process group, or user, as
19       indicated by which and who is obtained with the  getpriority  call  and
20       set   with  the  setpriority  call.   Which  is  one  of  PRIO_PROCESS,
21       PRIO_PGRP, or PRIO_USER, and who is interpreted relative  to  which  (a
22       process  identifier  for  PRIO_PROCESS,  process  group  identifier for
23       PRIO_PGRP, and a user ID for PRIO_USER).  A zero value of  who  denotes
24       the  current  process,  process group, or user.  Prio is a value in the
25       range -20 to 20.  The default priority is  0;  lower  priorities  cause
26       more favorable scheduling.
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28       The  getpriority  call  returns  the highest priority (lowest numerical
29       value) enjoyed by any of the specified processes.  The setpriority call
30       sets  the priorities of all of the specified processes to the specified
31       value.  Only the super-user may lower priorities.
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RETURN VALUE

34       Since getpriority can legitimately return the value -1, it is necessary
35       to  clear  the external variable errno prior to the call, then check it
36       afterward to determine if a -1 is an error or a legitimate value.   The
37       setpriority call returns 0 if there is no error, or -1 if there is.
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ERRORS

40       Getpriority and setpriority may return one of the following errors:
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42       [ESRCH]        No  process  was  located using the which and who values
43                      specified.
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45       [EINVAL]       Which  was  not  one  of  PRIO_PROCESS,  PRIO_PGRP,   or
46                      PRIO_USER.
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48       In  addition  to  the errors indicated above, setpriority may fail with
49       one of the following errors returned:
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51       [EPERM]        A process was located, but  neither  its  effective  nor
52                      real  user ID matched the effective user ID of the call‐
53                      er.
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55       [EACCES]       A non super-user attempted to lower a process priority.
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SEE ALSO

58       nice(1), fork(2), renice(8)
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624th Berkeley Distribution        May 22, 1986                   GETPRIORITY(2)
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