setpriority

NAME

       getpriority, setpriority - get/set program scheduling pri-
       ority

SYNOPSIS

       #include <sys/time.h>
       #include <sys/resource.h>

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

DESCRIPTION

       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  pro-
       cesses.   The  setpriority call sets the priorities of all
       of the specified processes to the specified  value.   Only
       the super-user may lower priorities.

RETURN VALUES

       Since getpriority 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 setpriority call returns
       0 if there is no error, or -1 if there is.

ERRORS

       ESRCH   No  process  was  located  using the which and who
               values specified.

       EINVAL  Which was not one of PRIO_PROCESS,  PRIO_PGRP,  or
               PRIO_USER.

       In  addition  to  the  errors indicated above, setpriority
       will fail if:

       EPERM  A process was located, but  neither  its  effective
              nor  real  user ID matched the effective user ID of
              the caller.

       EACCES A non super-user attempted to lower a process  pri-
              ority.

HISTORY

       These function calls appeared in BSD 4.2.

SEE ALSO

       nice(1), fork(2), renice(8)