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

Use this function:

function parse_crontab($time, $crontab)
         {$time=explode(' ', date('i G j n w', strtotime($time)));
          $crontab=explode(' ', $crontab);
          foreach ($crontab as $k=>&$v)
                  {$v=explode(',', $v);
                   foreach ($v as &$v1)
                           {$v1=preg_replace(array('/^\*$/', '/^\d+$/', '/^(\d+)\-(\d+)$/', '/^\*\/(\d+)$/'),
                                             array('true', '"'.$time[$k].'"==="\0"', '(\1<='.$time[$k].' and '.$time[$k].'<=\2)', $time[$k].'%\1===0'),
                                             $v1
                                            );
                           }
                   $v='('.implode(' or ', $v).')';
                  }
          $crontab=implode(' and ', $crontab);
          return eval('return '.$crontab.';');
         }
var_export(parse_crontab('2011-05-04 02:08:03', '*/2,3-5,9 2 3-5 */2 *'));
var_export(parse_crontab('2011-05-04 02:08:03', '*/8 */2 */4 */5 *'));

Edit Maybe this is more readable:

 &$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};");
    }

Usage: