说明：  你可以把本书作为教材,自学手册,或者你获得 shell 脚本技术的文档. 书中的练习和例子脚本中的注释将会与读者有更好的互动,但是最关键的前提是: 想真正学习脚本编程的唯一途径就是编写脚本
(You can use this book as a textbook, self-study manual, or documentation of your shell script The exercises in the book and the annotations in the example scripts will have better interaction with the readers, but the most important premise is that the: The only way to really learn scripting is to write scripts)