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

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

NNAAMMEE
     ggeettiittiimmeerr, sseettiittiimmeerr - get/set value of interval timer

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<ssyyss//ttiimmee..hh>>
     ##ddeeffiinnee IITTIIMMEERR__RREEAALL      00
     ##ddeeffiinnee IITTIIMMEERR__VVIIRRTTUUAALL   11
     ##ddeeffiinnee IITTIIMMEERR__PPRROOFF      22

     _i_n_t
     ggeettiittiimmeerr(_i_n_t _w_h_i_c_h, _s_t_r_u_c_t _i_t_i_m_e_r_v_a_l _*_v_a_l_u_e);

     _i_n_t
     sseettiittiimmeerr(_i_n_t _w_h_i_c_h, _s_t_r_u_c_t _i_t_i_m_e_r_v_a_l _*_v_a_l_u_e, _s_t_r_u_c_t _i_t_i_m_e_r_v_a_l _*_o_v_a_l_u_e);

DDEESSCCRRIIPPTTIIOONN
     The system provides each process with three interval timers, defined in
     <_s_y_s_/_t_i_m_e_._h>. The ggeettiittiimmeerr() call returns the current value for the
     timer specified in _w_h_i_c_h in the structure at _v_a_l_u_e. The sseettiittiimmeerr() call
     sets a timer to the specified _v_a_l_u_e (returning the previous value of the
     timer if _o_v_a_l_u_e is non-nil).

     A timer value is defined by the _i_t_i_m_e_r_v_a_l structure:

           struct itimerval {
                   struct  timeval it_interval;    /* timer interval */
                   struct  timeval it_value;       /* current value */
           };

     If _i_t___v_a_l_u_e is non-zero, it indicates the time to the next timer expira-
     tion.  If _i_t___i_n_t_e_r_v_a_l is non-zero, it specifies a value to be used in
     reloading _i_t___v_a_l_u_e when the timer expires.  Setting _i_t___v_a_l_u_e to 0 dis-
     ables a timer.  Setting _i_t___i_n_t_e_r_v_a_l to 0 causes a timer to be disabled
     after its next expiration (assuming _i_t___v_a_l_u_e is non-zero).

     Time values smaller than the resolution of the system clock are rounded
     up to this resolution (typically 10 milliseconds).

     The ITIMER_REAL timer decrements in real time.  A SIGALRM signal is de-
     livered when this timer expires.

     The ITIMER_VIRTUAL timer decrements in process virtual time.  It runs on-
     ly when the process is executing.  A SIGVTALRM signal is delivered when
     it expires.

     The ITIMER_PROF timer decrements both in process virtual time and when
     the system is running on behalf of the process.  It is designed to be
     used by interpreters in statistically profiling the execution of inter-
     preted programs.  Each time the ITIMER_PROF timer expires, the SIGPROF
     signal is delivered.  Because this signal may interrupt in-progress sys-
     tem calls, programs using this timer must be prepared to restart inter-
     rupted system calls.

NNOOTTEESS
     Three macros for manipulating time values are defined in <_s_y_s_/_t_i_m_e_._h>.
     _T_i_m_e_r_c_l_e_a_r sets a time value to zero, _t_i_m_e_r_i_s_s_e_t tests if a time value is
     non-zero, and _t_i_m_e_r_c_m_p compares two time values (beware that >= and <= do
     not work with this macro).

RREETTUURRNN VVAALLUUEESS
     If the calls succeed, a value of 0 is returned.  If an error occurs, the
     value -1 is returned, and a more precise error code is placed in the
     global variable _e_r_r_n_o.

EERRRROORRSS
     GGeettiittiimmeerr() and sseettiittiimmeerr() will fail if:

     [EFAULT]      The _v_a_l_u_e parameter specified a bad address.

     [EINVAL]      A _v_a_l_u_e parameter specified a time was too large to be han-
                   dled.

SSEEEE AALLSSOO
     select(2),  sigvec(2),  gettimeofday(2)

HHIISSTTOORRYY
     The ggeettiittiimmeerr function call appeared in 4.2BSD.

4.2 Berkeley Distribution        June 4, 1993                                2