4.4BSD/usr/share/man/cat2/adjtime.0

ADJTIME(2)                  BSD Programmer's Manual                 ADJTIME(2)

NNAAMMEE
     aaddjjttiimmee - correct the time to allow synchronization of the system clock

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<ssyyss//ttiimmee..hh>>

     _i_n_t
     aaddjjttiimmee(_s_t_r_u_c_t _t_i_m_e_v_a_l _*_d_e_l_t_a, _s_t_r_u_c_t _t_i_m_e_v_a_l _*_o_l_d_d_e_l_t_a);

DDEESSCCRRIIPPTTIIOONN
     AAddjjttiimmee() makes small adjustments to the system time, as returned by
     gettimeofday(2),  advancing or retarding it by the time specified by the
     timeval _d_e_l_t_a. If _d_e_l_t_a is negative, the clock is slowed down by incre-
     menting it more slowly than normal until the correction is complete.  If
     _d_e_l_t_a is positive, a larger increment than normal is used.  The skew used
     to perform the correction is generally a fraction of one percent.  Thus,
     the time is always a monotonically increasing function.  A time correc-
     tion from an earlier call to aaddjjttiimmee() may not be finished when aaddjjttiimmee()
     is called again.  If _o_l_d_d_e_l_t_a is non-nil, the structure pointed to will
     contain, upon return, the number of microseconds still to be corrected
     from the earlier call.

     This call may be used by time servers that synchronize the clocks of com-
     puters in a local area network.  Such time servers would slow down the
     clocks of some machines and speed up the clocks of others to bring them
     to the average network time.

     The call aaddjjttiimmee() is restricted to the super-user.

RREETTUURRNN VVAALLUUEESS
     A return value of 0 indicates that the call succeeded.  A return value of
     -1 indicates that an error occurred, and in this case an error code is
     stored in the global variable _e_r_r_n_o.

EERRRROORRSS
     AAddjjttiimmee() will fail if:

     [EFAULT]      An argument points outside the process's allocated address
                   space.

     [EPERM]       The process's effective user ID is not that of the super-
                   user.

SSEEEE AALLSSOO
     date(1),  gettimeofday(2),  timed(8),  timedc(8),

     R. Gusella, and S. Zatti, _T_S_P_: _T_h_e _T_i_m_e _S_y_n_c_h_r_o_n_i_z_a_t_i_o_n _P_r_o_t_o_c_o_l _f_o_r _U_N_I_X
     _4_._3_B_S_D.

HHIISSTTOORRYY
     The aaddjjttiimmee function call appeared in 4.3BSD.

4.3 Berkeley Distribution        June 4, 1993                                1