I want to escape a underscore in a filename with a backslash (\). So file_01.jpg would become file\_01.jpg.

I tried:

(replace-regexp-in-string "_" "\_"  "file_01.jpg" t t) 

but that produces file_01.jpg. And:

(replace-regexp-in-string "_" "\\_"  "file_01.jpg" t t)

gives file\\_01.jpg.

How can I insert a single backslash?

  • This possibly isn't the best way to do whatever it is that you need to do. What is it that requires escaped underscores in filenames? – phils Jul 19 '16 at 2:08

Your second example is actually correct. The resulting string contains a single backslash; it looks like a double backslash because it's printed as an Emacs Lisp string.

You can see this by converting the string into a list of one-character strings:

(mapcar 'string (replace-regexp-in-string "_" "\\_" "file_01.jpg" t t))

This returns:

("f" "i" "l" "e" "\\" "_" "0" "1" "." "j" "p" "g")

"\\" is a string with one character, a backslash. It is displayed with two backslashes because that's required by Emacs Lisp string syntax.

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  • The reason I want this is because I'm converting a org document to md with pandoc. The underscore interprets the following 01 as subscript. It works correct if I escape the underscore. "file\_01.jpg still gives me "file\" and then "01" as underscore. I guess i need something that gives me this list of one-character string: ("f" "i" "l" "e" "_" "0" "1" "." "j" "p" "g") – workspace Jun 24 '15 at 16:02
  • That would be (mapcar 'string "file_01.jpg"), if I'm understanding correctly. – legoscia Jun 24 '15 at 16:04
  • sorry I meant ("f" "i" "l" "e" "\_" "0" "1" "." "j" "p" "g"). – workspace Jun 24 '15 at 18:57
  • What should the "\_" string contain — a backslash, an underscore, or both? – legoscia Jun 24 '15 at 20:25
  • 1
    OK. I got it. sorry very new in elsip. when I insert the string with the double backslash i get the result i want. thank for your persitance! – workspace Jun 25 '15 at 8:45

Use (replace-string "_" "\\_"), maybe in combined with-temp-buffer to put the string in.

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