In emacs, how to strip CR (^M) and leave LF (^J) characters?

StackOverflow https://stackoverflow.com/questions/1171609

  •  19-09-2019
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Question

I am trying to use hexl mode to manually remove some special chars from a text file and don't see how to delete anything in hexl mode.

What I really want is to remove carriage return and keep linefeed characters. Is Hexl mode the right way to do this?

Was it helpful?

Solution

No need for hexl-mode for this. Just do a global-search-and-replace of ^J^M with ^J Works for me. :) Then save the file, kill the buffer, and revisit the file so the window shows the new file mode (Unix vs DOS).

OTHER TIPS

No need to find replace. Just use.

M-x delete-trailing-whitespace

You can also set the file encoding through

C-x RET f unix

Oops. That ^J^M needs to be entered as two literal characters. Use c-q c-j, c-q c-m and for the replacement string, use c-q c-j.

There's also a command-line tool called unix2dos/dos2unix that exists specifically to convert line endings.

Assuming you want a DOS encoded file to be changed into UNIX encoding, use M-x set-buffer-file-coding-system (C-x RET f) to set the coding-system to "unix" and save the file.

If you want to remove a carriage return (usually displayed as ^M) and leave the line feed. You can just visit the file w/out any conversion:

M-x find-file-literally /path/to/file

Because a file with carriage returns is generally displayed in DOS mode (hiding the carriage returns). The mode line will likely display (DOS) on the left side.

Once you've done that, the ^M will show up and you can delete them like you would any character.

You don't need to use hexl-mode. Instead:

  • open file in a way that shows you those ^M's. See M-x find-file-literally /path/to/file above. In XEmacs you can also do C-u C-x C-f and select binary encoding.
  • select the string you want replace and copy it using M-w
  • do M-% (query replace) and paste what you want to copy using C-y
  • present Enter when prompted to what replace it with
  • possible press ! now to replace all occurrences

The point is that even if you don't how to enter what you are trying to replace, you can always select/copy it.

(in hexl mode) I'm not sure that you can delete characters. I've always converted them to spaces or some other character, switched to the regular text editor, and deleted them there.

From http://www.xsteve.at/prg/emacs/xsteve-functions.el:

;02.02.2000
(defun xsteve-remove-control-M ()
  "Remove ^M at end of line in the whole buffer."
  (interactive)
  (save-match-data
    (save-excursion
      (let ((remove-count 0))
        (goto-char (point-min))
        (while (re-search-forward (concat (char-to-string 13) "$") (point-max) t)
          (setq remove-count (+ remove-count 1))
          (replace-match "" nil nil))
        (message (format "%d ^M removed from buffer." remove-count))))))

Add this to your .emacs and run it via M-x xsteve-remove-control-M or bind it to a easier key. It will strip the ^Ms in anymode.

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