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alarm(3)

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NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

       #include <unistd.h>

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

LIBRARY    [Toc]    [Back]

       Standard C Library (libc)

STANDARDS    [Toc]    [Back]

       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    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       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.

SEE ALSO    [Toc]    [Back]

      
      
       Functions: gettimer(3)

       Standards: standards(5)



                                                         alarm(3)
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