When you start Emacs, it normally attempts to load your init file. This is either a file named .emacs or .emacs.el in your home directory, or a file named init.el in a subdirectory named .emacs.d in your home directory. Whichever place you use, you can also compile the file (see Byte Compilation); then the actual file loaded will be .emacs.elc or init.elc.
The command-line switches ‘-q’, ‘-Q’, and ‘-u’
control whether and where to find the init file; ‘-q’ (and the
stronger ‘-Q’) says not to load an init file, while ‘-u
user’ says to load user's init file instead of yours.
See Entering Emacs. If neither
option is specified, Emacs uses the LOGNAME environment
variable, or the USER (most systems) or USERNAME (MS
systems) variable, to find your home directory and thus your init
file; this way, even if you have su'd, Emacs still loads your own init
file. If those environment variables are absent, though, Emacs uses
your user-id to find your home directory.
A site may have a default init file, which is the library
named default.el. Emacs finds the default.el file
through the standard search path for libraries (see How Programs Do Loading). The Emacs distribution does not come with this file; sites
may provide one for local customizations. If the default init file
exists, it is loaded whenever you start Emacs, except in batch mode or
if ‘-q’ (or ‘-Q’) is specified. But your own personal init
file, if any, is loaded first; if it sets inhibit-default-init
to a non-nil value, then Emacs does not subsequently load the
default.el file.
Another file for site-customization is site-start.el. Emacs loads this before the user's init file. You can inhibit the loading of this file with the option ‘--no-site-file’.
This variable specifies the site-customization file to load before the user's init file. Its normal value is
"site-start". The only way you can change it with real effect is to do so before dumping Emacs.
See Init File Examples, for examples of how to make various commonly desired customizations in your .emacs file.
This variable prevents Emacs from loading the default initialization library file for your session of Emacs. If its value is non-
nil, then the default library is not loaded. The default value isnil.
This normal hook is run, once, just before loading all the init files (the user's init file, default.el, and/or site-start.el). (The only way to change it with real effect is before dumping Emacs.)
This normal hook is run, once, just after loading all the init files (the user's init file, default.el, and/or site-start.el), before loading the terminal-specific library and processing the command-line action arguments.
This normal hook is run, once, just after handling the command line arguments, just before
term-setup-hook.
This variable holds the absolute file name of the user's init file. If the actual init file loaded is a compiled file, such as .emacs.elc, the value refers to the corresponding source file.
This variable holds the name of the .emacs.d directory. It is ordinarily ~/.emacs.d, but differs on some platforms.