Calculate when a cron job will be executed then next time

Question

I have a cron \"time definition\"

1 * * * * (every hour at xx:01)
2 5 * * * (every day at 05:02)
0 4 3 * * (every third day of the month at 04:00)
* 2 * * 5          


        

Answer 1

Thanks for posting this code. It definitely helped me out, even 6 years later.

Trying to implement I found a small bug.

date('i G j n w', $time) returns a 0 padded integer for the minutes.

Later in the code, it does a modulus on that 0 padded integer. PHP doesn't seem to handle this as expected.

$ php

3
0

As you can see, 08 % 5 returns 0, whereas 8 % 5 returns the expected 3. I couldn't find a non padded option for the date command. I tried fiddling with the {$time[$k]} % $1 === 0 line (like changing {$time[$k]} to ({$time[$k]}+0), but couldn't get it to drop the 0 padding during the modulus.

So, I ended up just changing the original value returned by the date function and removed the 0 by running $time[0] = $time[0] + 0;.

Here is my test.

 &$v) {
        $v = explode(',', $v);
        $regexps = array(
            '/^\*$/', # every 
            '/^\d+$/', # digit 
            '/^(\d+)\-(\d+)$/', # range
            '/^\*\/(\d+)$/' # every digit
        );
        $content = array(
            "true", # every
            "{$time[$k]} === $0", # digit
            "($1 <= {$time[$k]} && {$time[$k]} <= $2)", # range
            "{$time[$k]} % $1 === 0" # every digit
        );
        foreach ($v as &$v1)
            $v1 = preg_replace($regexps, $content, $v1);
            $v = '('.implode(' || ', $v).')';
    }
    $crontab = implode(' && ', $crontab);
    return eval("return {$crontab};");
}

for($i=0; $i<24; $i++) {
    for($j=0; $j<60; $j++) {
        $date=sprintf("%d:%02d",$i,$j);
        if (parse_crontab('*/5 * * * *',$date)) {
             print "$date yes\n";
        } else {
             print "$date no\n";
        }
    }
}

?>