UALARM(P) POSIX Programmer's Manual UALARM(P)PROLOG
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.
NAMEualarm - set the interval timer
SYNOPSIS
#include <unistd.h>
useconds_t ualarm(useconds_t useconds, useconds_t interval);
DESCRIPTION
The ualarm() function shall cause the SIGALRM signal to be generated
for the calling process after the number of realtime microseconds spec‐
ified 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 ter‐
minated.
Implementations may place limitations on the granularity of timer val‐
ues. 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()RETURN VALUE
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.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
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.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOalarm() , nanosleep() , setitimer() , sleep() , timer_create() ,
timer_delete() , timer_getoverrun() , the Base Definitions volume of
IEEE Std 1003.1-2001, <unistd.h>
COPYRIGHT
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 .
IEEE/The Open Group 2003 UALARM(P)
