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32 .\" @(#)getitimer.2 8.3 (Berkeley) 5/16/95
41 .Nd get/set value of interval timer
46 .Fd "#define ITIMER_REAL 0"
47 .Fd "#define ITIMER_VIRTUAL 1"
48 .Fd "#define ITIMER_PROF 2"
50 .Fn getitimer "int which" "struct itimerval *value"
52 .Fn setitimer "int which" "const struct itimerval *value" "struct itimerval *ovalue"
54 The system provides each process with three interval timers,
59 system call returns the current value for the timer specified in
65 system call sets a timer to the specified
67 (returning the previous value of the timer if
69 is not a null pointer).
71 A timer value is defined by the
74 .Bd -literal -offset indent
76 struct timeval it_interval; /* timer interval */
77 struct timeval it_value; /* current value */
83 is non-zero, it indicates the time to the next timer expiration.
86 is non-zero, it specifies a value to be used in reloading
88 when the timer expires.
91 to 0 disables a timer, regardless of the value of
95 to 0 causes a timer to be disabled after its next expiration (assuming
99 Time values smaller than the resolution of the
100 system clock are rounded up to this resolution
101 (typically 10 milliseconds).
105 timer decrements in real time.
109 delivered when this timer expires.
113 timer decrements in process virtual time.
114 It runs only when the process is executing.
118 is delivered when it expires.
122 timer decrements both in process virtual time and
123 when the system is running on behalf of the process.
125 to be used by interpreters in statistically profiling the execution
126 of interpreted programs.
133 Because this signal may interrupt in-progress
134 system calls, programs using this timer must be prepared to
135 restart interrupted system calls.
137 The maximum number of seconds allowed for
145 Three macros for manipulating time values are defined in
150 sets a time value to zero,
152 tests if a time value is non-zero, and
154 compares two time values.
168 argument specified a bad address.
172 argument specified a time that was too large
183 system call appeared in