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UALARM(3)		   Linux Programmer's Manual		     UALARM(3)

NAME
       ualarm -	schedule signal	after given number of microseconds

SYNOPSIS
       #include	<unistd.h>

       useconds_t ualarm(useconds_t usecs, useconds_t interval);

   Feature Test	Macro Requirements for glibc (see feature_test_macros(7)):

       ualarm():
	   Since glibc 2.12:
	       _BSD_SOURCE ||
		   (_XOPEN_SOURCE >= 500 ||
		       _XOPEN_SOURCE &&	_XOPEN_SOURCE_EXTENDED)	&&
		   !(_POSIX_C_SOURCE >=	200809L	|| _XOPEN_SOURCE >= 700)
	   Before glibc	2.12:
	       _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
	       _XOPEN_SOURCE &&	_XOPEN_SOURCE_EXTENDED

DESCRIPTION
       The ualarm() function causes the	signal SIGALRM to be sent to  the  in-
       voking process after (not less than) usecs microseconds.	 The delay may
       be lengthened slightly by any system activity or	by the time spent pro-
       cessing the call	or by the granularity of system	timers.

       Unless  caught  or  ignored,  the  SIGALRM  signal  will	 terminate the
       process.

       If the interval argument	is nonzero, further SIGALRM  signals  will  be
       sent every interval microseconds	after the first.

RETURN VALUE
       This  function  returns	the  number  of	microseconds remaining for any
       alarm that was previously set, or 0 if no alarm was pending.

ERRORS
       EINTR  Interrupted by a signal.

       EINVAL usecs or interval	is not	smaller	 than  1000000.	  (On  systems
	      where that is considered an error.)

ATTRIBUTES
   Multithreading (see pthreads(7))
       The ualarm() function is	thread-safe.

CONFORMING TO
       4.3BSD,	 POSIX.1-2001.	  POSIX.1-2001	marks  ualarm()	 as  obsolete.
       POSIX.1-2008 removes the	specification of ualarm().  4.3BSD, SUSv2, and
       POSIX do	not define any errors.

NOTES
       POSIX.1-2001  does not specify what happens if the usecs	argument is 0.
       On Linux	(and probably most other systems), the effect is to cancel any
       pending alarm.

       The  type useconds_t is an unsigned integer type	capable	of holding in-
       tegers in the range [0,1000000].	 On the	original  BSD  implementation,
       and in glibc before version 2.1,	the arguments to ualarm() were instead
       typed as	unsigned int.  Programs	will be	more portable  if  they	 never
       mention useconds_t explicitly.

       The  interaction	 of  this  function with other timer functions such as
       alarm(2),  sleep(3),   nanosleep(2),   setitimer(2),   timer_create(2),
       timer_delete(2),	  timer_getoverrun(2),	 timer_gettime(2),  timer_set-
       time(2),	usleep(3) is unspecified.

       This function is	obsolete.  Use setitimer(2) or POSIX  interval	timers
       (timer_create(2), etc.)	instead.

SEE ALSO
       alarm(2),    getitimer(2),   nanosleep(2),   select(2),	 setitimer(2),
       usleep(3), time(7)

COLOPHON
       This page is part of release 3.74 of the	Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       http://www.kernel.org/doc/man-pages/.

				  2013-12-23			     UALARM(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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