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getitimer.0
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1992-08-10
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GETITIMER(2) UNIX 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 nonnil).
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 nonzero, it indicates the time to the next timer expira
tion. If _i_t___i_n_t_e_r_v_a_l is nonzero, 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 nonzero).
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 inprogress 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
nonzero, 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 March 10, 1991 2