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   ualarm    ( 3 )

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Имя (Name)

ualarm - schedule signal after given number of microseconds

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Синопсис (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 <= 2.19: */ _BSD_SOURCE
           Before glibc 2.12:
               _BSD_SOURCE || _XOPEN_SOURCE >= 500

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Описание (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.

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Возвращаемое значение (Return value)

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

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Ошибки (Error)

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.)

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Атрибуты (Attributes)

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

       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │Interface                             │ Attribute     │ Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │ualarm()                              │ Thread safety │ MT-Safe │
       └──────────────────────────────────────┴───────────────┴─────────┘

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Стандарты (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.

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Примечание (Note)

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.

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Смотри также (See also)

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

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