_nnnn_iiii_cccc_eeee allows a process in the time-sharing scheduling class to change its
priority. The _ssss_cccc_hhhh_eeee_dddd______ssss_eeee_tttt_ssss_cccc_hhhh_eeee_dddd_uuuu_llll_eeee_rrrr and _ssss_cccc_hhhh_eeee_dddd_cccc_tttt_llll system calls are more
general interfaces to scheduler functions.
_nnnn_iiii_cccc_eeee adds the value of _i_n_c_r to the nice value of the calling process. A
process's nice value is a non-negative number for which a more positive
value results in lower CPU priority.
A maximum nice value of 39 and a minimum nice value of 0 are imposed by
the system. (The default nice value is 20.) Requests for values above
or below these limits result in the nice value being set to the
corresponding limit.
_EEEE_PPPP_EEEE_RRRR_MMMM _nnnn_iiii_cccc_eeee fails and does not change the nice value if _i_n_c_r is
negative or greater than 40 and the effective user ID of
the calling process is not super-user.
_EEEE_IIII_NNNN_VVVV_AAAA_LLLL _nnnn_iiii_cccc_eeee fails if called by a process in a scheduling class