Getting Started with Linux fifth day--shell script (bottom) looping and debugging of basic grammar

first, the circulation

　　1. Indefinite circulation

　　There are two kinds of forms:

 while [Condition] <== the state in parentheses  is the  beginning of the loop of the judgment do <==! Program paragraph  done <== do is the end of the loop

　　When the condition condition is established, the cycle is
The condition of condition is not tenable until it stops.

until [Condition]  Do Procedure paragraph  Done

　　When the condition condition is established, the cycle is terminated, otherwise it lasts
The program segment that is looping.

Getting Started with Linux fifth day--shell script (bottom) looping and debugging of basic grammar