|GETITIMER(3P)||POSIX Programmer's Manual||GETITIMER(3P)|
int getitimer(int which, struct itimerval *value); int setitimer(int which, const struct itimerval *restrict value, struct itimerval *restrict 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:
- 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.
- Decrements in real time. A SIGALRM signal is delivered when this timer expires.
- 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.
- 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:
- The which argument is not recognized.
The following sections are informative.
The Base Definitions volume of POSIX.1‐2017, <signal.h>, <sys_time.h>
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 .
|2017||IEEE/The Open Group|