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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 standards
  as follows:

  alarm(), ualarm(): XSH5.0

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

PARAMETERS
  seconds
      Specifies a number of real-time seconds.

  useconds
      Specifies a number of real-time microseconds.

  interval
      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:

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

SEE ALSO
  Functions: gettimer(3)

  Standards: standards(5)

Index for Section 3

Alphabetical listing for A

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