Unix commands(7)

                                      ....
                               done
　　           while-loop 将运行直到表达式测试为真。will run while the expression that we test for is true.
关键字"break" 用来跳出循环。而关键字”continue”用来不执行余下的部分而直接跳到下一个循环。
　　
                     for-loop表达式查看一个字符串列表 (字符串用空格分隔) 然后将其赋给一个变量：
                          1,   for var in ....; do
　                                ....
                                done
                       在下面的例子中，将分别打印ABC到屏幕上：
                            #!/bin/sh
                                    for var in A B C ; do
　                                echo "var is ＄var"
                                     done
                           2,   for (( 条件一; 条件二; 条件三 );do
                                ...
                                done