How can I detect that emacs-server is running from a shell prompt?

Question

I want to have my .bashrc detect if running emacsclient would work in lieu of running emacs. Basically:

if emacs_server_is_running; then
    EDITOR=emacsclient
    VISUAL=emacsclient
else
    EDITOR=emacs
    VISUAL=emacs
fi

What would I put in the emacs_server_is_running function to accomplish this aim?

Answer 1

You're making this too hard. From the the emacsclient(1) man page:

-a, --alternate-editor=EDITOR if the Emacs server is not running, run the specified editor instead. This can also be specified via the `ALTERNATE_EDITOR' environment variable. If the value of EDITOR is the empty string, then Emacs is started in daemon mode and emacsclient will try to connect to it.

Answer 2

From a shell script, you could do something like this:

emacsclient -ca false -e '(delete-frame)'

This will open a new emacs window then quickly close it, returning true on success. If no emacs server exists, the alternate editor is /bin/false, which returns false.

Answer 3

I read the answers, but none of this did fit my use case, where I did not want to start an server if not running and also wanted to avoid blocking forever.

Looking at the server-force-stop function in emacs, it simply deletes the server file in either server-auth-dir or server-socket-dir which in my case are /tmp/emacs1000/server or ~/.emacs.d/server.

Knowing this, to test if a server is running we can simply do:

test -e "/tmp/emacs1000/server" || test -e "~/.emacs.d/server"