Can .emacs location be specified with an environment variable? - linux

Question

I work in an environment where we all log in as ourselves, then sudo to a common user. (Bleah). I'm starting to use emacs and would like to specify my own .emacs file at launch. What I think I want is to specify the location of .emacs with an environment variable, but I don't see any way to do that in the emacs documentation. Is there one?
As an alternative, perhaps I need to learn elisp and conditionally load my own file out of the common .emacs file located in /home/common_user/.emacs? In my case, I already have an environment variable SUDO_USER set to my name 'lcuff', and an environment variable MY_CONF set to /foo/bar/blah/lcuff, wherein I'd like to store my own .emacs file. How would I do this?
Thoughts and advice appreciated.

Answer 1

See:
C-hig (emacs) Find Init RET
Failing anything else, you can specify $HOME for a command with env:
env HOME=/foo/bar/blah/lcuff emacs

Answer 2

Invoking emacs with the -u option will seek the init file for the given user, so
emacs -u Leonard
will run emacs with your emacs initialization file, even if you are logged in as another user.

Answer 3

You can tell emacs to load the init file of your choice by saying:
emacs -q -l /path/to/my/preferred/.emacs

Answer 4

It's a little bit tricky working out who emacs thinks you are. From info:
More precisely, Emacs first determines which user's init file to use.
It gets your user name from the environment variables LOGNAME and
USER; if neither of those exists, it uses effective user-ID. If that
user name matches the real user-ID, then Emacs uses `HOME'; otherwise,
it looks up the home directory corresponding to that user name in the
system's data base of users.
So I'd start first with finding out who emacs thinks you are, by starting emacs
without loading any init files:
emacs -q
and then find out where emacs thinks your init file is:
(locate-user-emacs-file "yourrealusername")
I think on a fresh home environment it will default to
~/.emacs.d/yourusername, but that should help you decide where best to place
the init file.
An important point is that it's pretty good practice to have an emacs user
directory rather than just a startup file. There is a heap of extra guff
that emacs needs to keep track of (package management, customized settings,
backup files, dictionary, manually inserted lisp code etc etc) and I find it extremely useful to put all
this stuff in the one spot. Emacs looks in ~/.emacs.d/init.el if it doesn't
see ~/.emacs or ~/.emacs.el on the system. Make sure you don't have ~/.emacs
still.
Create a new file called ~/.emacs.d/init.el
Put this in it:
(setq user-emacs-directory "~/.emacs.d/")
(message "This is my init.el file and noone elses!!!")
(inhibit-default-init) ;; there might be a default.el lurking somewhere
If emacs got your username and home right, you can then restart with:
emacs -u therealme
or, if it stuffs up the environment variables
env HOME=/this/is/my/home USER=blah emacs
There just might be a site-start.el somewhere that might get loaded before
your init.el. If you suspect this, loading emacs with the --no-site-file
option will nuke this.