nice ?priorityincr?

          Change or return the process priority.  If priorityincr
          is  omitted,  the  current  priority  is  returned.  If
          priorityincr is positive, it is added  to  the  current
          priority  level,  up  to a system defined maximum (nor-
          mally 19),

          Negative priorityincr values cumulatively increase  the
          program's  priority  down  to  a system defined minimum
          (normally -19); increasing priority with negative nice-
          ness values will only work for the superuser.

          The new priority is returned.

          The nice command is not available on Windows 95/NT.

          This command is provided by Extended Tcl.