php man page for ualarm

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:
	       (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
		   || /* Glibc since 2.19: */ _DEFAULT_SOURCE
		   || /* Glibc versions <= 2.19: */ _BSD_SOURCE
	   Before glibc 2.12:
	       _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       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 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; see signal(7).

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

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       +----------+---------------+---------+
       |Interface | Attribute	  | Value   |
       +----------+---------------+---------+
       |ualarm()  | Thread safety | MT-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 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_settime(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 4.15 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 https://www.kernel.org/doc/man-pages/.

								    2017-09-15								 UALARM(3)