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GETITIMER(3P) POSIX Programmer's Manual GETITIMER(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
getitimer, setitimer — get and set value of interval timer
#include <sys/time.h>
int getitimer(int which, struct itimerval *value);
int setitimer(int which, const struct itimerval *restrict value,
struct itimerval *restrict ovalue);
The getitimer() function shall store the current value of the timer
specified by which into the structure pointed to by value. The
setitimer() function shall set the timer specified by which to the
value specified in the structure pointed to by value, and if ovalue
is not a null pointer, store the previous value of the timer in the
structure pointed to by ovalue.
A timer value is defined by the itimerval structure, specified in
<sys/time.h>. If it_value is non-zero, it shall indicate the time to
the next timer expiration. If it_interval is non-zero, it shall
specify a value to be used in reloading it_value when the timer
expires. Setting it_value to 0 shall disable a timer, regardless of
the value of it_interval. Setting it_interval to 0 shall disable a
timer after its next expiration (assuming it_value is non-zero).
Implementations may place limitations on the granularity of timer
values. For each interval timer, if the requested timer value
requires a finer granularity than the implementation supports, the
actual timer value shall be rounded up to the next supported value.
An XSI-conforming implementation provides each process with at least
three interval timers, which are indicated by the which argument:
ITIMER_PROF 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 interpreted programs. Each
time the ITIMER_PROF timer expires, the SIGPROF signal
is delivered.
ITIMER_REAL Decrements in real time. A SIGALRM signal is delivered
when this timer expires.
ITIMER_VIRTUAL
Decrements in process virtual time. It runs only when
the process is executing. A SIGVTALRM signal is
delivered when it expires.
The interaction between setitimer() and alarm() or sleep() is
unspecified.
Upon successful completion, getitimer() or setitimer() shall return
0; otherwise, −1 shall be returned and errno set to indicate the
error.
The setitimer() function shall fail if:
EINVAL The value argument is not in canonical form. (In canonical
form, the number of microseconds is a non-negative integer
less than 1000000 and the number of seconds is a non-negative
integer.)
The getitimer() and setitimer() functions may fail if:
EINVAL The which argument is not recognized.
The following sections are informative.
None.
Applications should use the timer_gettime() and timer_settime()
functions instead of the obsolescent getitimer() and setitimer()
functions, respectively.
None.
The getitimer() and setitimer() functions may be removed in a future
version.
alarm(3p), exec(1p), sleep(3p), timer_getoverrun(3p)
The Base Definitions volume of POSIX.1‐2008, signal.h(0p),
sys_time.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 GETITIMER(3P)
Pages that refer to this page: sys_time.h(0p), alarm(3p), exec(3p), pselect(3p), setitimer(3p), sleep(3p)