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

       ualarm - schedule signal after given number of microseconds

       #include <unistd.h>

       useconds_t ualarm(useconds_t usecs, useconds_t interval);

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

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

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

       Unless  caught  or  ignored,  the  SIGALRM  signal  will	 terminate the

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

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

       EINTR  Interrupted by a signal.

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

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

       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.

       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
       integers 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       This function is obsolete.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.

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

       This page is part of release 3.65 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at

				  2013-12-23			     UALARM(3)

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