参考自http://codingstandards.iteye.com/blog/780524
1.while true do command; done
2.while : do command; done
3.while [1] do command; done
4.while [0] do command done
5.while 条件 do command; done
shell实现死循环
原文：http://www.cnblogs.com/yrpen/p/4060222.html
