alarm man page on DigitalUNIX

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alarm(3)							      alarm(3)

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

SYNOPSIS
       #include <unistd.h>

       unsigned int alarm(
	       unsigned int seconds ); useconds_t ualarm(
	       unseconds_t useconds,
	       unseconds_t interval );

LIBRARY
       Standard C Library (libc)

STANDARDS
       Interfaces  documented on this reference page conform to industry stan‐
       dards 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  parame‐
       ter  has elapsed. When the interval parameter is nonzero, timeout noti‐
       fication 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; other‐
       wise  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 follow‐
       ing conditions:

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

SEE ALSO
       Functions: gettimer(3)

       Standards: standards(5)

								      alarm(3)
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