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usleep(3) [bsd man page]

USLEEP(3)						     Library Functions Manual							 USLEEP(3)

NAME
usleep - suspend execution for interval SYNOPSIS
usleep(useconds) unsigned useconds; DESCRIPTION
The current process is suspended from execution for the number of microseconds specified by the argument. The actual suspension time may be an arbitrary amount longer because of other activity in the system or because of the time spent in processing the call. The routine is implemented by setting an interval timer and pausing until it occurs. The previous state of this timer is saved and restored. If the sleep time exceeds the time to the expiration of the previous timer, the process sleeps only until the signal would have occurred, and the signal is sent a short time later. This routine is implemented using setitimer(2); it requires eight system calls each time it is invoked. A similar but less compatible function can be obtained with a single select(2); it would not restart after signals, but would not interfere with other uses of setitimer. SEE ALSO
setitimer(2), getitimer(2), sigpause(2), ualarm(3), sleep(3), alarm(3) NOTES (PDP-11) On the PDP-11, setitimer(2) rounds the number of microseconds up to seconds resolution, therefore usleep doesn't give you any more resolu- tion than sleep(3). Select(2) offers clock resolution (usually 60Hz in the U.S.A. and 50Hz elsewhere) and so should be used instead. 4.3 Berkeley Distribution August 26, 1988 USLEEP(3)

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UALARM(3)						     Library Functions Manual							 UALARM(3)

NAME
ualarm - schedule signal after specified time SYNOPSIS
unsigned ualarm(value, interval) unsigned value; unsigned interval; DESCRIPTION
This is a simplified interface to setitimer(2). Ualarm causes signal SIGALRM, see signal(3C), to be sent to the invoking process in a number of microseconds given by the value argument. Unless caught or ignored, the signal terminates the process. 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. after value microseconds have passed). Because of scheduling delays, resumption of execution of when the signal is caught may be delayed an arbitrary amount. The longest speci- fiable delay time (on the vax) is 2147483647 microseconds. The return value is the amount of time previously remaining in the alarm clock. SEE ALSO
getitimer(2), setitimer(2), sigpause(2), sigvec(2), signal(3C), sleep(3), alarm(3), usleep(3) NOTES (PDP-11) On the PDP-11, setitimer(2) rounds the number of microseconds up to seconds resolution, therefore ualarm doesn't give you any more resolu- tion than alarm(3). 4.3 Berkeley Distribution August 26, 1988 UALARM(3)
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