ualarm - schedule signal after given number of microseconds

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

       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.

EINTR  Interrupted by a signal; see signal(7).

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

       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 unsignedint.  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       This function is obsolete.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.

       Standard C library (libc, -lc)

       ualarm - schedule signal after given number of microseconds

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

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

Linux man-pages 6.9.1                              2024-05-02                                          ualarm(3)

       None.

#include<unistd.h>useconds_tualarm(useconds_tusecs,useconds_tinterval);

   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