UALARM(3) Library Functions Manual UALARM(3)

ualarm — set the interval timer


#include <unistd.h>

useconds_t ualarm(useconds_t useconds, useconds_t interval);

The ualarm () function shall cause the SIGALRM signal to be generated for the calling process after the number of realtime microseconds specified by the argument has elapsed. When the interval argument is non-zero, repeated timeout notification occurs with a period in microseconds specified by the interval argument. If the notification signal, SIGALRM, is not caught or ignored, the calling process is terminated.

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.

Interactions between ualarm () and any of the following are unspecified:

alarm()
nanosleep()
setitimer()
timer_create()
timer_delete()
timer_getoverrun()
timer_gettime()
timer_settime()
sleep()

The ualarm () function shall return the number of microseconds remaining from the previous ualarm () call. If no timeouts are pending or if ualarm () has not previously been called, ualarm () shall return 0.

No errors are defined.

None.

Applications are recommended to use nanosleep(3) if the Timers option is supported, or setitimer(3), timer_create(3), timer_delete(3), timer_getoverrun(3), timer_gettime(3), or timer_settime(3) instead of this function.

None.

None.

alarm(3), nanosleep(3), setitimer(3), sleep(3), timer_create(3), timer_delete(3), timer_getoverrun(3), the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), <unistd.h>

First released in Issue 4, Version 2.

Moved from X/OPEN UNIX extension to BASE.

This function is marked obsolescent.

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January 1, 2004 posix.fail