4.3BSD-UWisc/man/cat2/adjtime.2

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



NAME
     adjtime - correct the time to allow synchronization of the
     system clock

SYNOPSIS
     #include <sys/time.h>

     adjtime(delta, olddelta)
     struct timeval *delta;
     struct timeval *olddelta;

DESCRIPTION
     _A_d_j_t_i_m_e makes small adjustments to the system time, as
     returned by _g_e_t_t_i_m_e_o_f_d_a_y(2), advancing or retarding it by
     the time specified by the timeval _d_e_l_t_a.  If _d_e_l_t_a is nega-
     tive, the clock is slowed down by incrementing 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 frac-
     tion of one percent.  Thus, the time is always a monotoni-
     cally increasing function.  A time correction from an ear-
     lier call to _a_d_j_t_i_m_e may not be finished when _a_d_j_t_i_m_e is
     called again.  If _o_l_d_d_e_l_t_a is non-zero, then 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 computers 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 _a_d_j_t_i_m_e(2) is restricted to the super-user.

RETURN VALUE
     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.

ERRORS
     The following error codes may be set in _e_r_r_n_o:

     [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.

SEE ALSO
     date(1), gettimeofday(2), timed(8), timedc(8),
     _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, R.



Printed 12/27/86          May 15, 1986                          1






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



     Gusella and S. Zatti






















































Printed 12/27/86          May 15, 1986                          2