ADJTIME(2) ADJTIME(2) NAME adjtime - correct the time to allow synchronization of the system clock SYNOPSIS #include 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 negative, the clock is slowed down by incrementing it more slowly than normal until the correction is com‐ plete. 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 correction from an earlier 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 struc‐ ture 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. Gusella and S. Zatti 4.3 Berkeley Distribution May 15, 1986 ADJTIME(2)