setitimer(2) - NetBSD Manual Pages

GETITIMER(2)              NetBSD System Calls Manual              GETITIMER(2)


NAME
getitimer, setitimer -- get/set value of interval timer
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/time.h> int getitimer(int which, struct itimerval *value); int setitimer(int which, const struct itimerval * restrict value, struct itimerval * restrict ovalue);
DESCRIPTION
The system provides each process with three interval timers, defined in <sys/time.h>. The getitimer() call returns the current value for the timer specified in which in the structure at value. The setitimer() call sets a timer to the specified value, returning the previous value of the timer if ovalue is not NULL. A timer value is defined by the itimerval structure: struct itimerval { struct timeval it_interval; /* timer interval */ struct timeval it_value; /* current value */ }; If it_value is non-zero, it indicates the time to the next timer expira- tion. If it_interval is non-zero, it specifies a value to be used in reloading it_value when the timer expires. Setting it_value to 0 dis- ables a timer. Setting it_interval to 0 causes a timer to be disabled after its next expiration (assuming it_value is non-zero). The which parameter specifies the type of the timer: ITIMER_REAL timer decrements in real time. This timer is affected by adjtime(2) and settimeofday(2). A SIGALRM signal is delivered when this timer expires. ITIMER_VIRTUAL timer decrements in process virtual time. It runs only when the process is executing. A SIGVTALRM signal is delivered when it expires. ITIMER_PROF timer decrements both in process virtual time and when the system is running on behalf of the process. It is designed to be used by inter- preters in statistically profiling the execution of interpreted programs. Each time the ITIMER_PROF timer expires, the SIGPROF signal is delivered. Because this signal may interrupt in-progress system calls, programs using this timer must be prepared to restart interrupted system calls. ITIMER_MONOTONIC timer decrements in monotonic time. This timer is not affected by adjtime(2) and settimeofday(2). A SIGALRM signal is delivered when this timer expires. Note that: · Time values smaller than the resolution of the system clock are rounded up to this resolution (typically 10 milliseconds). · The interaction between setitimer() and alarm(3) or sleep(3) is unspecified by the specification.
RETURN VALUES
If the calls succeed, a value of 0 is returned. If an error occurs, the value -1 is returned, and a more precise error code is placed in the global variable errno.
ERRORS
Both functions may fail if: [EFAULT] The value parameter specified a bad address. [EINVAL] The which parameter was not a known timer type, or the value parameter specified a time that was too large to be handled.
SEE ALSO
gettimeofday(2), select(2), sigaction(2), itimerval(3), timeradd(3)
STANDARDS
The functions conform to IEEE Std 1003.1-2001 (``POSIX.1''). The later IEEE Std 1003.1-2008 (``POSIX.1'') revision however marked both as obso- lescent, recommending the use of timer_gettime(2) and timer_settime(2) instead.
HISTORY
The getitimer() function call appeared in 4.2BSD. The ITIMER_MONOTONIC functionality appeared in NetBSD 6.0. NetBSD 8.0 October 27, 2011 NetBSD 8.0

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