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GETPRIORITY(2)                System Calls Manual               GETPRIORITY(2)

       getpriority, setpriority - get/set process nice value

       #include <&lt;sys/time.h>&gt;
       #include <&lt;sys/resource.h>&gt;

       int getpriority(which, who)
       int which, who;

       int setpriority(which, who, niceval)
       int which, who, niceval;

       The  nice  value  of a process, process group, or user, as indicated by
       which and who is obtained with the getpriority() call and set with  the
       setpriority() call.  Process nice values can range from -20 through 19.
       The default nice value is 0; lower nice  values  cause  more  favorable

       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

       The  getpriority()  call returns the lowest numerical nice value of any
       of the specified processes.  The setpriority() call sets the nice  val-
       ues  of  all of the specified processes to the value specified by nice-
       val.  If niceval is less than -20, a value of -20 is  used;  if  it  is
       greater  than  19,  a value of 19 is used.  Only the super-user may use
       negative nice values.

       Since getpriority() can legitimately return the value -1, it is  neces-
       sary to clear the external variable errno prior to the call, then check
       it afterward to determine if a -1 is an error or a legitimate value.

       setpriority() returns:

       0      on success.

       -1     on failure and sets errno to indicate the error.

       getpriority() and setpriority() may set errno to:

       EINVAL         which  was  not  one  of  PRIO_PROCESS,  PRIO_PGRP,   or

       ESRCH          No  process  was  located using the which and who values

       In addition to the errors indicated above, setpriority() may fail  with
       one of the following errors returned:

       EACCES         The  call to setpriority() would have changed a process'
                      nice value to a value lower than its current value,  and
                      the  effective user ID of the process executing the call
                      was not that of the super-user.

       EPERM          A process was located, but  neither  its  effective  nor
                      real  user ID matched the effective user ID of the call-
                      er, and neither the effective nor the real  user  ID  of
                      the process executing setpriority() was super-user.

       nice(1), ps(1), fork(2V), nice(3v) renice(8)

       It is not possible for the process executing setpriority() to lower any
       other process down to its current nice value, without requiring  super-
       user privileges.

       These  system calls are misnamed.  They get and set the nice value, not
       the kernel scheduling priority.   nice(1)  discusses  the  relationship
       between nice value and scheduling priority.

                                21 January 1990                 GETPRIORITY(2)