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28 .\" @(#)getitimer.2 8.3 (Berkeley) 5/16/95
37 .Nd get/set value of interval timer
42 .Fd "#define ITIMER_REAL 0"
43 .Fd "#define ITIMER_VIRTUAL 1"
44 .Fd "#define ITIMER_PROF 2"
46 .Fn getitimer "int which" "struct itimerval *value"
48 .Fn setitimer "int which" "const struct itimerval *value" "struct itimerval *ovalue"
50 The system provides each process with three interval timers,
55 system call returns the current value for the timer specified in
61 system call sets a timer to the specified
63 (returning the previous value of the timer if
65 is not a null pointer).
67 A timer value is defined by the
70 .Bd -literal -offset indent
72 struct timeval it_interval; /* timer interval */
73 struct timeval it_value; /* current value */
79 is non-zero, it indicates the time to the next timer expiration.
82 is non-zero, it specifies a value to be used in reloading
84 when the timer expires.
87 to 0 disables a timer, regardless of the value of
91 to 0 causes a timer to be disabled after its next expiration (assuming
95 Time values smaller than the resolution of the
96 system clock are rounded up to this resolution
97 (typically 10 milliseconds).
101 timer decrements in real time.
105 delivered when this timer expires.
109 timer decrements in process virtual time.
110 It runs only when the process is executing.
114 is delivered when it expires.
118 timer decrements both in process virtual time and
119 when the system is running on behalf of the process.
121 to be used by interpreters in statistically profiling the execution
122 of interpreted programs.
129 Because this signal may interrupt in-progress
130 system calls, programs using this timer must be prepared to
131 restart interrupted system calls.
133 The maximum number of seconds allowed for
141 Three macros for manipulating time values are defined in
146 sets a time value to zero,
148 tests if a time value is non-zero, and
150 compares two time values.
164 argument specified a bad address.
168 argument specified a time that was too large
179 system call appeared in