Unix/Linux实战:嵌入文档使用攻略

　　三、技术基础

　　我们采用Red Hat Linux和Unix下面广泛使用的BASH来编写脚本。首先讲解有关Here Documents的语法基础和基本使用方法。

　　3.1 语法结构

　　在命令行中执行man bash，可以找到BASH手册中有关Here Documents的语法定义，其一般形式如下：

　　#man bash

　　Here Documents

　　This type of redirection instructs the shell to read input from the

　　current source until a line containing only word (with no trailing

　　blanks) is seen. All of the lines read up to that point are then used

　　as the standard input for a command.

　　The format of here-documents is:

　　<<[-]word

　　here-document

　　delimiter

　　No parameter expansion, command substitution, arithmetic expansion, or

　　pathname expansion is performed on word. If any characters in word are

　　quoted, the delimiter is the result of quote removal on word, and the

　　lines in the here-document are not expanded. If word is unquoted, all

　　lines of the here-document are subjected to parameter expansion, com-

　　mand substitution, and arithmetic expansion. In the latter case, the

　　character sequence is ignored, and must be used to quote

　　the characters , $, and `.

　　If the redirection operator is <<-, then all leading tab characters are

　　stripped from input lines and the line containing delimiter. This

　　allows here-documents within shell scripts to be indented in a natural