CODEWITHSUNDEEP
windowsshellemacscarriage-returnlinefeed
CodeSmith
CodeSmith

Reputation: 113

How can I change which line ending style is used in the emacs shell (Carriage return / line feed)?

I am working on a windows 10 machine using Emacs and plink to connect to a Linux development server. I am able to start a shell in Emacs using M-x shell and ssh to the server with plink server

When I press enter on my keyboard it's like I have pressed enter twice rather than once username@server>ls<enter> file1 file2 file3 username@server> username@server>

I initially thought this had something to do with extraneous escape characters for the terminal as other questions have indicated. Opening a windows command prompt and ssh'ing to the server with plink output these extraneous characters and I was able to remove them with the following variables in my bashrc:

export PROMPT_COMMAND="" export PS1="\u@\H:\W> export TERM=""

The windows command prompt now properly displayed the plink session with no extraneous escape characters. Despite this, the Emacs shell still seemed to press enter twice for one press.

Next, I assumed there was a problem with the characters that were being sent by the enter key.

running showkey -a seems to explain the problem:

In a real putty window and in the Windows command prompt I got the following showkey output while in a ssh connection to the server:

showkey -a Press any keys - Ctrl-D will terminate this program ^M 13 0015 0x0d

in the Emacs shell I get this output

showkey -a Press any keys - Ctrl-D will terminate this program ^M^J 13 0015 0x0d 10 0012 0x0a

It seems that the Emacs shell is sending a carriage return as well as a line feed when I press enter (the DOS line ending format). It makes sense then that enter is "pressed twice." Is there any way to change this behavior in the shell? I have seen the use of set-buffer-file-coding-system to tell Emacs to use Unix, Windows or Mac line endings. but this doesn't seem to work for me since I am in a shell.

Upvotes: 2

Views: 913

Answers (1)

phils
phils

Reputation: 73274

For each inferior process, Emacs applies independent coding systems for the process input and process output.

In your case the coding system for input to the process will be a "dos" system, resulting in the CRLF pair being sent to the process for EOLs.

You can use M-x set-buffer-process-coding-system to change these input/output coding systems interactively for the current buffer. Bound by default to C-xRETp

You could also use a hook to do so automatically for certain modes. e.g.:

(add-hook 'shell-mode-hook 'my-shell-mode-hook)
(defun my-shell-mode-hook ()
  "Custom `shell-mode' behaviours."
  (set-buffer-process-coding-system 'utf-8-unix 'iso-latin-1-unix))

As per the interactive prompts, the first argument is "Coding-system for output from the process" and the second is "Coding-system for input to the process".

See C-hig (emacs)Communication Coding for more information.

Upvotes: 1

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