getpriority(2) - NetBSD Manual Pages

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GETPRIORITY(2)            NetBSD System Calls Manual            GETPRIORITY(2)


NAME

     getpriority, setpriority -- get/set program scheduling priority


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <sys/resource.h>

     int
     getpriority(int which, id_t who);

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


DESCRIPTION

     The scheduling priority of the process, process group, or user, as indi-
     cated 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

     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() 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 prior-
                        ity.


SEE ALSO

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


HISTORY

     The getpriority() function call appeared in 4.2BSD.

NetBSD 6.1.2                    April 25, 2004                    NetBSD 6.1.2