沙盒

Shell Operation:	The basic operation of the shell. shell的基本操作。
Quoting:	How to remove the special meaning from characters. 如何删除字符的特殊含义。
Comments:	How to specify comments. 如何指定注释。

When the shell reads input, it proceeds through a sequence of operations. If the input indicates the beginning of a comment, the shell ignores the comment symbol (‘#’), and the rest of that line.

当shell读取输入时，它是按照一定顺序的操作来完成的。如果输入始于一个注释，则shell将忽略改行注释符号（"#"）及其后的字符。

Otherwise, roughly speaking, the shell reads its input and divides the input into words and operators, employing the quoting rules to select which meanings to assign various words and characters.

The shell then parses these tokens into commands and other constructs, removes the special meaning of certain words or characters, expands others, redirects input and output as needed, executes the specified command, waits for the command’s exit status, and makes that exit status available for further inspection or processing.