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, this signal will terminate the process.
If the interval argument is nonzero, further SIGALRM signals will be sent
every interval microseconds after the first.
The type useconds_t is an unsigned integer type capable of holding
integers in the range [0,1000000]. This type is defined by
<sys/types.h> included by <unistd.h> but glibc
defines it only when _XOPEN_SOURCE has a value not less than 500, or both
_XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED are defined. Programs will be more
portable if they never mention this type explicitly.
The interaction of this function with other timer functions such as
alarm(), sleep(), nanosleep(), setitimer(),
timer_create(), timer_delete(), timer_getoverrun(),
timer_gettime(), timer_settime(), usleep() is
This function is obsolete. Use nanosleep(2) or setitimer(2)