Set up Emacs on Windows to start a single instance and open files in the existing instance

Question

I am particularly interested in the full Windows experience including:

• Automatically starting a server if one is not already started
• How to call emacs so that it utilizes the server (e.g. from command line or third party tools)
• Context menu support (e.g. right-click on a file and allow it to be sent to emacs for viewing and editing)

Is such support available out of the box anywhere?

Answer 1

Automatically starting a server if one is not already started

This should be the same for any Emacs build. Add this snippet to your .emacs or .emacs.d/init.el.

(require 'server)
(unless (server-running-p)
  (server-start)) 

And then just start emacs by running the runemacs.exe executable that comes with the build.

How to call emacs so that it utilizes the server (e.g. from command line or third party tools)

Emacs' Windows build comes with an emacsclientw.exe executable in the bin/ directory. Use the full path to that executable as your editor of choice on any third party tools you need to configure.

Context menu support (e.g. right-click on a file and allow it to be sent to emacs for viewing and editing)

1. Right click on a file, select Open With -> Select Default Program.
2. In the window that pops up, navigate to your emacsclientw.exe executable mentioned above and choose it.
3. If you don't want Emacs to be the default, do steps 1 and 2 again, choosing a different program as the default.

emacsclientw.exe will now always be an option in the context menu.

Answer 2

Automatically starting a server if one is not already started

I highly recommend setting an environment variable for ALTERNATE_EDITOR to runemacs.exe. This way you can always call emacsclient even if there is no server. Just add (server-start) to your init file. When a server does not exist emacsclient calls the ALTERNATE_EDITOR which is emacs in our case. Since emace starts up a server in the init file, any new calls to emacsclient will be instantaneous.

How to call emacs so that it utilizes the server (e.g. from command line or third party tools)

Use emacsclientw.exe -c -n "your_file" to open your_file . The -c argument creates a new graphical frame and -n allows you to close the frame without losing server state. You can even call it without a filename to open the *Scratch* buffer. Works from a desktop shortcut also. Using emacsclient.exe (note the missing w) will pop up a command prompt for a few seconds everytime you call it.

Adding to context menu

Emacswiki has a nice page on adding Emacs to the context menu here. It involves editing the registry node HKEY_CLASSES_ROOT\* to add an action to open with emacs.

Answer 3

Others have answered the server part. Here is what I do, to get UNIX / GNU/Linux-like utilities such as grep and diff:

1. Install Cygwin (one-time operation).
2. Load cygwin-mount.el.
3. Load setup-cygwin.el.

However, be aware that there are different versions of Cygwin. I use an older version (dunno which one - hard to tell, AFAICT). Dunno whether you will have problems with recent versions.

See also:

• Emacs on Windows with Cygwin
• Ediff on Windows