cron jobs

How do you set up a cron to execute on every half second?

I have a script that I want to run every half second in PHP and I want the cron job to handle it

Thanks

Cron only works down to 1 minute resolution.
You might have to use usleep() or microtime() and have the script organise its own timing.

HalfaBee

As HalfaBee said. When I wanted to run something every 15 seconds I had 0-59 * or whatever in crontab calling a php script that said:

DoThings();
sleep(15);
DoThings();
sleep(15);
DoThings();
sleep(15);
DoThings();

function DoThings();
{

code

}

Don't know if you're asking for trouble trying to do things every half second, what with the overhead of loading the the interpreter and stuff.

If you need that this process must be executed always, you have to run it in background (&) in your system.

And yes, the best way is doing an infinite looping with a pause.

while(1) {
 ....
 usleep(500000);
}

Note: usleep() works with microseconds, so 1 second = 1000000 micro seconds.