Source can be browsed here and downloaded from github.com:

git clone git://github.com/nandra/ctimer.git ctimer

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/types.h>
#include <signal.h>
#include <unistd.h>

#define NSEC_PER_SEC 1000000000L

#define timerdiff(a,b) ((float)((a)->tv_sec - (b)->tv_sec) + \
((float)((a)->tv_nsec - (b)->tv_nsec))/NSEC_PER_SEC)

static struct timespec prev = {.tv_sec=0,.tv_nsec=0};
static int count = 5;

void handler( signo )
{
struct timespec now;

clock_gettime(CLOCK_MONOTONIC, &now);
printf("[%d]Diff time:%lf\n", count, timerdiff(&now, &prev));
prev = now;
count --;
}

int main(int argc, char *argv[])
{
int i = 0;
timer_t t_id;

struct itimerspec tim_spec = {.it_interval= {.tv_sec=1,.tv_nsec=10000},
.it_value = {.tv_sec=1,.tv_nsec=10000}};

struct sigaction act;
sigset_t set;

sigemptyset( &set );
sigaddset( &set, SIGALRM );

act.sa_flags = 0;
act.sa_mask = set;
act.sa_handler = &handler;

sigaction( SIGALRM, &act, NULL );

if (timer_create(CLOCK_MONOTONIC, NULL, &t_id))
perror("timer_create");

if (timer_settime(t_id, 0, &tim_spec, NULL))
perror("timer_settime");

clock_gettime(CLOCK_MONOTONIC, &prev);

for (; ; )
{
if(count == 0)
break;
}

return 0;
}

Program explanation:

- define sigaction for signal SIGALRM which is received if timer expired

- create timer (timer is not started)

- set timer (this function start timer)

- wait for 5 periods and then exit

In output you should see values for 5 period of timer. Timer is set to 1 seconds and 1us interval.

Note: for compiling please add to CFLAGS option: -lrt (realtime library).

Source for download: test_timerc

Marek