how to set environment variables={EDITOR, VISUAL} to prefer running emacs?

Question

my usecase

I'm currently running GNU Emacs version=24.3.1 graphically (i.e., under GNOME/X though started from a script invoked from a gnome-terminal running bash) on a Debian Linux. Just now I was using commandline abcde to rip audio CDs when its terminal suddenly opened an instance of The Editor Which Must Not Be Named (to resolve an MP3 tagging question). I realized that, when I setup the box I'm currently using, I failed to set either of the bash environment variables EDITOR or VISUAL in my .bashrc.

what I want

I nearly always have an graphical/X instance of Emacs running. If I'm not running Emacs, I probably have a good reason not to (e.g., a problem with my config files, or that I'm running in a tty). So I'm wondering, how to set EDITOR or VISUAL so that an application that wants to open an editor does one of the following, in descending order of preference:

1. If I already have an instance of Emacs running (i.e., pgrep -l emacs | wc -l -> 1): open the thing to be edited in a new buffer in the running Emacs.
2. If I do not have an instance of Emacs running (i.e., pgrep -l emacs | wc -l -> 0): start a new instance of emacs -nw -q in the terminal.

If I can't get both those preferences, or if there's a reason why I should deprecate one or both, feel free to recommend Something Completely Different.

solution

emacsclient is finicky about its arguments (TODO: put a bug on it!), but that can be worked-around:

1. Per Francesco's suggestion I made ~/bin/emacs-nw-q.sh (and of course set mode=executable)

   ### Purely for use with `emacsclient`: see https://emacs.stackexchange.com/a/8089/5444
   emacs -nw -q $@
   

2. Added a stanza to the end of my .bashrc:

   if [[ -z "${EDITOR}" ]] ; then
     export ALTERNATE_EDITOR="${HOME}/bin/emacs-nw-q.sh"
     export EDITOR='emacsclient'
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

With this, and

• a running "emacs+server" (i.e., a previously-running graphical Emacs, in which I have done M-x server-start): an edit-seeking application successfully opens a buffer in the running emacs on the desired file, and killing that buffer unpauses the edit-seeking application.
• no running emacs+server: an edit-seeking application opens a "bare-bones" Emacs in its same terminal, as desired, with a buffer open to the desired file, and killing that buffer returns control to the edit-seeking application.

how I failed

I'm putting a stanza at the end of my .bashrc: each of the stanzas I've tried is listed below, with the resulting error. To test each stanza, after I [edit, save] .bashrc (via emacs -nw -q ~/.bashrc in a separate gnome-terminal tab), I open a fresh gnome-terminal tab to exercise it.

1. With a running emacs (and after M-x server-start), following fails with emacsclient: unrecognized option '-''

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR="emacsclient --alternate-editor='emacs -nw -q'"
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

2. With a running emacs+server, following fails with emacsclient: unrecognized option '-"'

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR='emacsclient --alternate-editor="emacs -nw -q"'
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

3. With no running emacs, following fails with emacsclient: error executing alternate editor ""emacs"". So I guess --alternate-editor just won't take a quoted argument?

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR='emacsclient --alternate-editor="emacs"'
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

4. With no running emacs, following starts a brand-new graphical emacs with everything (including full desktop, which I don't want for this usecase) ... but it gets worse: after I save and kill the buffer opened by the caller app, that caller app just sits there!

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR='emacsclient --alternate-editor=emacs'
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

5. With no running emacs, following fails with emacsclient: error executing alternate editor """"

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR='emacsclient --alternate-editor=""' # sorta suggested by erikstokes at above link
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

6. With no running emacs, following fails with emacsclient: error executing alternate editor """" (i.e., same as previous)

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR='emacsclient -a""'
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

7. With no running emacs, following fails with emacsclient: error executing alternate editor "''"

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR="emacsclient -a''"
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

8. With no running emacs, following

   if [[ -z "${EDITOR}" ]] ; then
     export EDITOR='emacsclient'
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

   fails with

   emacsclient: No socket or alternate editor.  Please use:
   --socket-name
   --server-file      (or environment variable EMACS_SERVER_FILE)
   --alternate-editor (or environment variable ALTERNATE_EDITOR)
   

9. With no running emacs, following fails with emacsclient: error executing alternate editor "emacs -nw -q"

   if [[ -z "${EDITOR}" ]] ; then
     export ALTERNATE_EDITOR='emacs -nw -q'
     export EDITOR='emacsclient'
   fi
   if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
     export VISUAL="${EDITOR}"
   fi
   

10. Per Francesco's suggestion I made ~/bin/emacs-nw-q.sh

    ### Purely for use with `emacsclient`: see https://emacs.stackexchange.com/a/8089/5444
    emacs -nw -q
    

    and changed my .bashrc stanza to

    if [[ -z "${EDITOR}" ]] ; then
      export ALTERNATE_EDITOR="${HOME}/bin/emacs-nw-q.sh"
      export EDITOR='emacsclient'
    fi
    if [[ -n "${EDITOR}" && -z "${VISUAL}" ]] ; then
      export VISUAL="${EDITOR}"
    fi
    

    Good news: with running emacs (and after M-x server-start), an edit-seeking application successfully opens a buffer in the running emacs on the desired file, and killing that buffer returns control to the edit-seeking application.

    More good news: with no running emacs+server, the edit-seeking application opens a "bare-bones" Emacs in its same terminal, as desired.

    Bad news: with no running emacs+server, the "bare-bones" Emacs does not open the needed file in a buffer. It does create the following buffers: *GNU Emacs*, *Messages*, *scratch* ... but not the needed buffer.

Answer 1

Although it is not clearly documented in its man page, emacsclient doesn't seem to accept a full command (i.e. program + arguments) as the alternate editor, only a program.

You could write a small shell script:

#!/bin/bash
exec emacs -q -nw "$@"

and use it as the alternate editor:

export EDITOR='emacsclient -a PATH_TO_YOUR_SCRIPT'

Answer 2

emacsclient has a -a option which lets you specify an alternate editor to use if there is not an emacs process with a running server.

So emacsclient -a emacs may do what you want.

The alternate editor can also be specified to emacsclient via the ALTERNATE_EDITOR environment variable.

As for which of EDITOR or VISUAL to set: EDITOR was traditionally used for line oriented editors such as ed or ex while VISUAL was for screen oriented editors such as emacs or vi. Thus you probably do not have to set EDITOR. I would however suggest setting both as a "belt-and-suspenders" measure as which variable is used is up to the program that is launching your editor, check with its documentation to find out which it would use.