Manual Pages  — UALARM

The ualarm() function waits a count of microseconds before asserting the terminating signal SIGALRM. System activity or time used in processing the call may cause a slight delay.

If the interval argument is non-zero, the SIGALRM signal will be sent to the process every interval microseconds after the timer expires (e.g.amp; after microseconds number of microseconds have passed).

Due to setitimer(2) restriction the maximum number of microseconds and interval is limited to 100000000000000 (in case this value fits in the unsigned integer).