getpriority(2)                4 BSD                getpriority(2)



NAME
     getpriority, setpriority - get/set program scheduling prior-
     ity

SYNOPSIS
     #include <sys/resource.h>

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

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

DESCRIPTION
     The nice value 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   process id
          PRIO_PGRP      process group id
          PRIO_USER      user id

     and who is interpreted relative to which (a process identif-
     ier for PRIO_PROCESS, process group identifier for
     PRIO_PGRP, and a user ID for PRIO_USER).  Nice is a value in
     the range -20 to 20.  The default nice value is 0; lower
     nice values cause more favorable scheduling.  The internal
     scheduling priority for a process is a function of the
     specified nice value.  An internal scheduling priority of a
     higher value corresponds to more favorable scheduling.

     When the INTERACTIVE_CLASS option is configured in the sys-
     tem, a process whose nice value is between -20 and -16 has a
     static priority, that is; it does not have its internal
     scheduling priority altered by the system.  A process whose
     nice value is greater than -16 may have its internal
     scheduling priority altered by the system.

     When the INTERACTIVE_CLASS option is not configured, the
     internal scheduling priority of a process is never altered.
     See the CX/RT Reference Manual for more information about
     scheduling.

     Modifying the nice value of a process results in the
     process's time quantum (see setquantum(2)) being reset to
     the system default value corresponding to the new priority
     value.

     The getpriority call returns the highest nice value (lowest
     numerical value) enjoyed by any of the specified processes.
     The setpriority call sets the nice values of all of the
     specified processes to the specified value.  Only the



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getpriority(2)                4 BSD                getpriority(2)



     super-user or a user with the ACC_SETPRI access vector may
     lower nice values.

RETURN VALUE
     Since getpriority can legitimately return the value -1, it
     is necessary 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.  The setpriority call returns 0
     if there is no error, or -1 if there is.

ERRORS
     getpriority and setpriority may return one of the following
     errors:

     [ESRCH]        No process(es) were 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 may
     fail with one of the following errors returned:

     [EACCES]       A process was located, but neither its effec-
                    tive nor real user ID matched the effective
                    user ID of the caller.

     [EACCES]       A non super-user attempted to change a pro-
                    cess priority to a negative value or the user
                    does not have the ACC_SETPRI access vector.
                    (If access vectors are configured).

SEE ALSO
     nice(1), fork(2), setquantum(2), renice(1)





















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