nice(2)

NAME
     nice - set program priority

SYNOPSIS
     #include <unistd.h>

     int nice(int incr)

DESCRIPTION
     The scheduling priority of the process is augmented  by  incr.   Positive
     priorities  get  less service than normal.  Priority 10 is recommended to
     users who wish to execute long-running programs  without  flak  from  the
     administration.

     Negative increments are ignored except on behalf of the super-user.   The
     priority is limited to the range -20 (most urgent) to 20 (least).

     The priority of a process is passed to a child process by fork(2).  For a
     privileged  process  to  return to normal priority from an unknown state,
     nice should be called successively with arguments -40 (goes  to  priority
     -20 because of truncation), 20 (to get to 0).

     If a CPU-bound process at nice level 0 gets one tick from the  scheduler,
     then  a  CPU-bound  process  at nice level n is entitled to 2 ** (-n / 2)
     ticks, which boils down to 1/32 ticks at nice level 10, and 1/1024  ticks
     at nice level 20.  Compared to other systems the effect of the Minix nice
     is quite strong.

SEE ALSO
     nice(1).