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34 .Nd get/set value of interval timer
39 .Fd "#define ITIMER_REAL 0"
40 .Fd "#define ITIMER_VIRTUAL 1"
41 .Fd "#define ITIMER_PROF 2"
43 .Fn getitimer "int which" "struct itimerval *value"
45 .Fn setitimer "int which" "const struct itimerval *value" "struct itimerval *ovalue"
47 The system provides each process with three interval timers,
52 system call returns the current value for the timer specified in
58 system call sets a timer to the specified
60 (returning the previous value of the timer if
62 is not a null pointer).
64 A timer value is defined by the
67 .Bd -literal -offset indent
69 struct timeval it_interval; /* timer interval */
70 struct timeval it_value; /* current value */
76 is non-zero, it indicates the time to the next timer expiration.
79 is non-zero, it specifies a value to be used in reloading
81 when the timer expires.
84 to 0 disables a timer, regardless of the value of
88 to 0 causes a timer to be disabled after its next expiration (assuming
92 Time values smaller than the resolution of the
93 system clock are rounded up to this resolution
94 (typically 10 milliseconds).
98 timer decrements in real time.
102 delivered when this timer expires.
106 timer decrements in process virtual time.
107 It runs only when the process is executing.
111 is delivered when it expires.
115 timer decrements both in process virtual time and
116 when the system is running on behalf of the process.
118 to be used by interpreters in statistically profiling the execution
119 of interpreted programs.
126 Because this signal may interrupt in-progress
127 system calls, programs using this timer must be prepared to
128 restart interrupted system calls.
130 The maximum number of seconds allowed for
138 Three macros for manipulating time values are defined in
143 sets a time value to zero,
145 tests if a time value is non-zero, and
147 compares two time values.
161 argument specified a bad address.
165 argument specified a time that was too large
182 revision however marked both functions as obsolescent,
183 recommending the use of
191 system call appeared in