UALARM(3P)                                          POSIX Programmer's Manual                                         UALARM(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       ualarm - 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 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()

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 ALSO
       alarm(), nanosleep(), setitimer(), sleep(), timer_create(), timer_delete(), timer_getoverrun(), the Base Definitions vol-
       ume 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    UALARM(3P)