sh for

for ((i=1;i<=5;i++));do ping 192.168.1.$i;done 
for ((i=1;i<=i++;i++));do echo 192.168.1.$i;done

from http://hi.baidu.com/baijunhui/blog/item/fb358339fdf1cdfb3b87ce85.html

原来脚本如此的naive，整的我都不敢用了。