Emacs: Quoting Regex in Emacs Lisp Code vs Command Prompt

In emacs lisp code, regular expression is a String, thus it follows string syntax. It needs to be enclosed by double quote string delimiters like "this". Backslash is escapte character. "\n" means newline, \t means a tab character, and "\\" means a literal single backslash.

When calling a emacs command that prompt for a regular expression, do not type the "string delimiters", nor adding extra backslash, because emacs auto convert your input to string. But because it is not a string, it does not understand string syntax such as \n or \t. You must use a literal newline or tab. [see Emacs: How to Insert a Tab Character or Newline].

For example, in emacs lisp, regex for matching a literal dot is "\\."

(re-search-forward "\\.jpg")

;; cat.jpg

but in a interactive call, you type \.

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