Creating a timer

The first step is to create the timer with timer_create():

#include <time.h>
#include <sys/siginfo.h>

int
timer_create (clockid_t clock_id,
              struct sigevent *event,
              timer_t *timerid);

The clock_id argument tells the timer_create() function which time base you're creating this timer for. This is a POSIX thing—POSIX says that on different platforms you can have multiple time bases, but that every platform must support at least the CLOCK_REALTIME time base. Under QNX Neutrino, the time bases to choose from include the following:

• CLOCK_REALTIME
• CLOCK_SOFTTIME
• CLOCK_MONOTONIC

For now, we'll ignore CLOCK_SOFTTIME and CLOCK_MONOTONIC (even though CLOCK_MONOTONIC is the best choice for timers), but we will come back to them in the “Other clock sources” section, below.