1GETITIMER(3P) POSIX Programmer's Manual GETITIMER(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 getitimer, setitimer — get and set value of interval timer
13
15 #include <sys/time.h>
16 int getitimer(int which, struct itimerval *value);
18 int setitimer(int which, const struct itimerval *restrict value,
19 struct itimerval *restrict ovalue);
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22 The getitimer() function shall store the current value of the timer
23 specified by which into the structure pointed to by value. The
24 setitimer() function shall set the timer specified by which to the
25 value specified in the structure pointed to by value, and if ovalue is
26 not a null pointer, store the previous value of the timer in the struc‐
27 ture pointed to by ovalue.
28 A timer value is defined by the itimerval structure, specified in
30 <sys/time.h>. If it_value is non-zero, it shall indicate the time to
31 the next timer expiration. If it_interval is non-zero, it shall spec‐
32 ify a value to be used in reloading it_value when the timer expires.
33 Setting it_value to 0 shall disable a timer, regardless of the value of
34 it_interval. Setting it_interval to 0 shall disable a timer after its
35 next expiration (assuming it_value is non-zero).
36 Implementations may place limitations on the granularity of timer val‐
38 ues. For each interval timer, if the requested timer value requires a
39 finer granularity than the implementation supports, the actual timer
40 value shall be rounded up to the next supported value.
41 An XSI-conforming implementation provides each process with at least
43 three interval timers, which are indicated by the which argument:
44 ITIMER_PROF Decrements both in process virtual time and when the sys‐
46 tem is running on behalf of the process. It is designed
47 to be used by interpreters in statistically profiling the
48 execution of interpreted programs. Each time the
49 ITIMER_PROF timer expires, the SIGPROF signal is deliv‐
50 ered.
51 ITIMER_REAL Decrements in real time. A SIGALRM signal is delivered
53 when this timer expires.
54 ITIMER_VIRTUAL
56 Decrements in process virtual time. It runs only when the
57 process is executing. A SIGVTALRM signal is delivered
58 when it expires.
59 The interaction between setitimer() and alarm() or sleep() is unspeci‐
61 fied.
62
64 Upon successful completion, getitimer() or setitimer() shall return 0;
65 otherwise, -1 shall be returned and errno set to indicate the error.
66
68 The setitimer() function shall fail if:
69 EINVAL The value argument is not in canonical form. (In canonical form,
71 the number of microseconds is a non-negative integer less than
72 1000000 and the number of seconds is a non-negative integer.)
73 The getitimer() and setitimer() functions may fail if:
75 EINVAL The which argument is not recognized.
77 The following sections are informative.
79
81 None.
82
84 Applications should use the timer_gettime() and timer_settime() func‐
85 tions instead of the obsolescent getitimer() and setitimer() functions,
86 respectively.
87
89 None.
90
92 The getitimer() and setitimer() functions may be removed in a future
93 version.
94
96 alarm(), exec, sleep(), timer_getoverrun()
97 The Base Definitions volume of POSIX.1‐2017, <signal.h>, <sys_time.h>
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101 Portions of this text are reprinted and reproduced in electronic form
102 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
103 table Operating System Interface (POSIX), The Open Group Base Specifi‐
104 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
105 Electrical and Electronics Engineers, Inc and The Open Group. In the
106 event of any discrepancy between this version and the original IEEE and
107 The Open Group Standard, the original IEEE and The Open Group Standard
108 is the referee document. The original Standard can be obtained online
109 at http://www.opengroup.org/unix/online.html .
110 Any typographical or formatting errors that appear in this page are
112 most likely to have been introduced during the conversion of the source
113 files to man page format. To report such errors, see https://www.ker‐
114 nel.org/doc/man-pages/reporting_bugs.html .
115IEEE/The Open Group 2017 GETITIMER(3P)