alarm(3)						     Library Functions Manual							  alarm(3)

NAME

       alarm, ualarm - Sets or changes the timeout of interval timers.

LIBRARY

       Standard C Library (libc)

SYNOPSIS

       #include <unistd.h>

       unsigned int alarm(
	       unsigned int seconds);

       useconds_t ualarm(
	       useconds_t useconds,
	       useconds_t interval);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       alarm(), ualarm(): XSH5.0

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Specifies a number of real-time seconds.  Specifies a number of real-time microseconds.	Specifies the interval for repeating the timer.

DESCRIPTION

       The  alarm()  function is used to obtain notification of a timeout after the number of real-time seconds specified by the seconds parameter
       has elapsed.  At some time after seconds seconds have elapsed, a signal is delivered to the process.  Each call resets the timer to the new
       value.	A  value  of 0 (zero) disables the timer.  When the notification signal is caught or ignored, no action takes place; otherwise the
       calling process is terminated.  The alarm() function uses the ITIMER_REAL interval timer.

       The ualarm() function is used to obtain notification of a timeout after the number of real-time	microseconds  specified  by  the  useconds
       parameter  has  elapsed.  When the interval parameter is nonzero, timeout notification occurs after the number of microseconds specified by
       the interval parameter has been added to the useconds parameter.  When the notification signal is caught or ignored, no action takes place;
       otherwise  the  calling process is terminated.  The ualarm() function is the simplified interface to the setitimer() function, and uses the
       ITIMER_REAL interval timer.

NOTES

       The alarm() and ualarm() functions are supported for multithreaded applications.

       Although the alarm() and ualarm() functions are reentrant, it should be noted that just as the second of two calls from a single thread	to
       alarm() resets the timer, this is also true if two calls are made from different threads.

RETURN VALUES

       If  there  is  a  previous alarm() request with time remaining, the alarm() function returns a non-zero value that is the number of seconds
       until the previous request would have generated a SIGALRM signal.  Otherwise, alarm() returns 0 (zero).

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

ERRORS

       The alarm() function sets errno to the specified values for the following conditions:

       [Tru64 UNIX]  The seconds parameter specifies a value greater than 100,000,000.

RELATED INFORMATION

       Functions: gettimer(3)

       Standards: standards(5) delim off

																	  alarm(3)