Re: ^M characters

[Xah <xahlee@gmail.com>]

On Oct 22, 1:29 pm, Corey Foote <coreyfo...@hotmail.com> wrote:
> I copied some text into an email buffer, but
> each line ends with a funny colored character that looks like ^M. What are
> these characters? How can I remove them without having to manually delete each
> one? And how can I insert one myself?

^M is a standard notation for the ascii 13 char named Carriage Return.

Today, this notation has fallen out of use, unfamiliar to probably 99%
of professional programers.

For detail, see:

The Confusion of Emacs's Keystroke Representation
http://xahlee.org/emacs/keystroke_rep.html

When you paste some code involving different EOL char, most editor
deal with this by simply converting them to your current EOL. Usually
they have a preference setting to indicate whether you want this to
happen automatically or literal. I think emacs should also adapt this
behavior.

To replace these unprintable chars, you can use any of the emacs's
find/replace command (e.g. “query-replace”), and type Ctrl+q when you
want to input unprintable or un-typable chars. Alternatively, you can
change the buffer's file encoding. See:

Q: How to change file line endings between Mac/Dos/Unix?

A: Open the file, then do “Alt+x set-buffer-file-coding-system” (Ctrl-
x RET f). Give it a value of mac, dos, unix. Then, when you save the
file, it'll be saved with the proper encoding for newlines.

Note: Unixes (including Linuxes and Mac OS X) uses LF (ascii 10; line
feed) for newline. Mac OS Classic uses CR (ascii 13; carriage return)
for newline. (Mac OS X prefers LF but accepts CR too) Windows uses CR
followed by LF ("\r\n") for its newline char. See wikipedia newline↗
for detail.

To do it batch on a list of files, use the following lisp code:

(defun to-unix-eol (fpath)
  "Change file's line ending to unix convention."
  (let (mybuffer)
    (setq mybuffer (find-file fpath))
    (set-buffer-file-coding-system 'unix) ; or 'mac or 'dos
    (save-buffer)
    (kill-buffer mybuffer)
   )
)

(mapc 'to-unix-eol
 (list
"~/jane/myfile1"
"~/jane/myfile2"
"~/jane/myfile3"
; ...
  )
)

To use the code, first edit the list of files above. Then, select all
the code, type “Alt+x eval-region”. That's it.

If you want the function to work on marked files in dired, then use
the following code:

(defun dired-2unix-marked-files ()
  "Change to unix line ending for marked (or next arg) files."
  (interactive)
  (mapc 'to-unix-eol (dired-get-marked-files))
)

Select the code and do “Alt+x eval-region”, then “Alt+x dired”, then
press “m” to mark the files you want, then do “Alt+x dired-dos2unix-
marked-files”.

  Xah
∑ http://xahlee.org/

☄