Elisp: Regex Backslash in Lisp Code
Backslash in Emacs Lisp Regex String
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".
In string, backslash is escape character.
"\n"- Newline.
"\t"- Tab.
"\""- Literal double quote.
"[chars]"- Any of chars
"[\t\n ]+"- Sequence of {tab, newline, space}.
"\\[abc\\]"- Literal square bracket with abc inside.
"(abc)"- Literal parenthesis and text.
"\\(pattern\\)"- Capture pattern.
"\\1"- First captured pattern. Used in replacement.
"\\2"- Second captured pattern. Used in replacement.
- When a file is opened in Emacs, newline is always
\n, regardless whether your file is from {Unix, Windows, Mac}.
Example: Quoting Regex in Emacs Lisp Code
Here's example, suppose you have this text:
src="cat.jpg"
When you call a command such as
list-matching-lines
, you can type the regex in the prompt. Example:
src="\([^"]+?\)"
But in lisp code, the same regex needs to have many backslash escapes, like this:
(re-search-forward "src=\"\\([^\"]+?\\)\"" )