If the single quotation mark is the outermost quote, no variables are expanded.

如果最外边的引号是单引号，那么不展开变量。

youdao

The single quotation mark ('), however, does not provide this functionality.

但是，单引号(')不提供此功能。

youdao

If you start a string with a single quotation mark, you must end with a single quotation mark, and vice versa.

如果字符串是以单引号开始，那么必须以单引号结束，反之亦然。

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