running a script from cron every second

问题

i have a script which i am running from browser with meta refresh and it workd without any issue in browser but it will not work in cron so what i can do to run every second from cron? i know with sleep i can but i have to create several cron tab in cron job and every time i have to run the script

with sleep how can i run this script every 5 sec.

<meta http-equiv="refresh" content="5;url=test.php">
<?php
    $res = mysql_query("SELECT * FROM tableA where st='0' order by id asc LIMIT 1");
    $row = mysql_fetch_array($res);

    $link= $row['wl'];

    function getTitle($Url){
        $str = file_get_contents($Url);
        if(strlen($str)>0){
        preg_match("/\<\/td\><\/tr\><tr\><td colspan\=2\>(.*)\<\/td\>/",$str,$title);

            return $title[1];
        }
    }
    getTitle($link);
?>

回答1:

Just add to your crontab

* * * * * for i in {0..59}; do curl http://your.domain.zone/page.html && sleep 1; done;

for added because cron could not run faster than once per minute.

回答2:

Minimum call interval is 1 minute for cron

If you need more frequent calls, you have multiple choices:

Create a daemon which is launched and then inside daemon you can put your own checks/sleep etc.
You can listen to file system events to trigger processing of whatever tasks you need
You can still use meta/js to "reload" page with combination of cron, but in that case you need to use headless browser such as phantomjs to handle your page and reloads properly. So you would be opening your "page" once a minute, and page would do 60/5=12 reloads itself using either js or meta tag.

clearly 3 is the worst. normally you would go either with option (1) or (2), depending on your system requirements.

来源：https://stackoverflow.com/questions/19606095/running-a-script-from-cron-every-second

标签

php

cron

crontab