[root@iZ2531r338hZ www]# crontab -e
* * * * * curl http://www.baidu.com
* * * * * sleep 3; curl http://www.baidu.com
* * * * * sleep 6; curl http://www.baidu.com
* * * * * sleep 9; curl http://www.baidu.com
* * * * * sleep 12; curl http://www.baidu.com
* * * * * sleep 15; curl http://www.baidu.com
* * * * * sleep 18; curl http://www.baidu.com
* * * * * sleep 21; curl http://www.baidu.com
* * * * * sleep 24; curl http://www.baidu.com
* * * * * sleep 27; curl http://www.baidu.com
* * * * * sleep 30; curl http://www.baidu.com
* * * * * sleep 33; curl http://www.baidu.com
* * * * * sleep 36; curl http://www.baidu.com
* * * * * sleep 39; curl http://www.baidu.com
* * * * * sleep 42; curl http://www.baidu.com
* * * * * sleep 45; curl http://www.baidu.com
* * * * * sleep 48; curl http://www.baidu.com
* * * * * sleep 51; curl http://www.baidu.com
* * * * * sleep 54; curl http://www.baidu.com
* * * * * sleep 57; curl http://www.baidu.com
