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:
(_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
The ualarm() function causes the signal
SIGALRM to be sent to the invoking process after (not
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.
interval argument is nonzero, further
SIGALRM signals will be sent every
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.
Interrupted by a signal; see signal(7).
interval is not smaller than 1000000. (On
systems where that is considered an error.)
POSIX.1-2001 does not specify what happens if the
argument is 0. On Linux (and probably most other systems), the effect is
to cancel any pending alarm.
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
Programs will be more portable if they never mention
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.
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