说明：  非常详细介绍linux_unix shelld的语法和编程方法、技巧。内容全面、已整理为单个PDF文件，文字清晰简洁，很适合Shell编程人员学习、参考。
(Linux_unix shelld very detailed description of the syntax and programming methods, techniques. Is comprehensive, has compiled into a single PDF file, text clear and concise, very suitable to learn Shell programming, reference.)