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ualarm(3) — Linux manual page

ualarm(3) Library Functions Manual ualarm(3)

NAME top

 ualarm - schedule signal after given number of microseconds

LIBRARY top

 Standard C library (libc, -lc)

SYNOPSIS top

 #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 >= 2.19: */ _DEFAULT_SOURCE
 || /* glibc <= 2.19: */ _BSD_SOURCE
 Before glibc 2.12:
 _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION top

 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 top

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

ERRORS top

 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 top

 For an explanation of the terms used in this section, see
 attributes(7).
 ┌──────────────────────────────────────┬───────────────┬─────────┐
 │ Interface │ Attribute │ Value │
 ├──────────────────────────────────────┼───────────────┼─────────┤
 │ ualarm() │ Thread safety │ MT-Safe │
 └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

 None.

HISTORY top

 4.3BSD, POSIX.1-2001. POSIX.1-2001 marks it as obsolete. Removed
 in POSIX.1-2008.
 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 glibc 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 top

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

COLOPHON top

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 user-space interface documentation) project. Information about
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 for this manual page, see
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 This page was obtained from the tarball man-pages-6.10.tar.gz
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 2025年02月02日. If you discover any rendering problems in this HTML
 version of the page, or you believe there is a better or more up-
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 man-pages@man7.org
Linux man-pages 6.10 2024年07月23日 ualarm(3)

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Pages that refer to this page: usleep(3)

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