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22.2.2 Parsing Rules

When operating in non-POSIX mode, `shlex` will try to obey to the following rules.

- Quote characters are not recognized within words (`Do"Not"Separate` is parsed as the single word `Do"Not"Separate`);
- Escape characters are not recognized;
- Enclosing characters in quotes preserve the literal value of all characters within the quotes;
- Closing quotes separate words (`"Do"Separate` is parsed as `"Do"` and `Separate`);
- If `whitespace_split` is `False`, any character not declared to be a word character, whitespace, or a quote will be returned as a single-character token. If it is `True`, `shlex` will only split words in whitespaces;
- EOF is signaled with an empty string (`''`);
- It's not possible to parse empty strings, even if quoted.

When operating in POSIX mode, `shlex` will try to obey to the following parsing rules.

- Quotes are stripped out, and do not separate words (`"Do"Not"Separate"` is parsed as the single word `DoNotSeparate`);
- Non-quoted escape characters (e.g. "`\`") preserve the literal value of the next character that follows;
- Enclosing characters in quotes which are not part of `escapedquotes` (e.g. "`'`") preserve the literal value of all characters within the quotes;
- Enclosing characters in quotes which are part of `escapedquotes` (e.g. "`"`") preserves the literal value of all characters within the quotes, with the exception of the characters mentioned in `escape`. The escape characters retain its special meaning only when followed by the quote in use, or the escape character itself. Otherwise the escape character will be considered a normal character.
- EOF is signaled with a `None` value;
- Quoted empty strings (`''`) are allowed;