NAME    [Toc]    [Back]

     getpriority, setpriority - get/set program scheduling priority

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #include <sys/resource.h>

     int
     getpriority(int which, int who);

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

DESCRIPTION    [Toc]    [Back]

     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. A value
     of 19 or 20 will schedule a process only when nothing at priority <= 0 is
     runnable.

     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.

RETURN VALUES    [Toc]    [Back]

     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    [Toc]    [Back]

     getpriority() and setpriority() will fail if:

     [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 priority.

SEE ALSO    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

     The getpriority() function call appeared in 4.2BSD.

BSD                              June 4, 1993                              BSD