GETPRIORITY(2)

NAME

     getpriority, setpriority -- get/set program scheduling priority

LIBRARY

     Standard C Library (libc, -lc)

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 indi-
     cated by which and who is obtained with the getpriority() system call and
     set with the setpriority() system call.  The which argument 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.  The prio argument is a
     value in the range -20 to 20.  The default priority is 0; lower priori-
     ties cause more favorable scheduling.

     The getpriority() system call returns the highest priority (lowest numer-
     ical value) enjoyed by any of the specified processes.  The setpriority()
     system 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() function returns the value 0 if successful; otherwise
     the value -1 is returned and the global variable errno is set to indicate
     the error.

ERRORS

     The getpriority() and setpriority() system calls will fail if:

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

     [EINVAL]		The which argument 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() system call appeared in 4.2BSD.