IEEE/The Open Group
This manual page is part of the POSIX Programmer’s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
ualarm - set the interval timer
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 useconds 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.
The following sections are informative.
Applications are recommended to use nanosleep() if the Timers option is supported, or setitimer(), timer_create(), timer_delete(), timer_getoverrun(), timer_gettime(), or timer_settime() instead of this function.
alarm(), nanosleep(), setitimer(), sleep(), timer_create(), timer_delete(), timer_getoverrun(), the Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .