Here are some examples of doing certain commonly desired things with Lisp expressions:
load-path. You can then put
Lisp libraries that are not included with Emacs in this directory, and
load them with M-x load-library. See Lisp Libraries.
(add-to-list 'load-path "/path/to/lisp/libraries")
(setq c-tab-always-indent nil)
Here we have a variable whose value is normally t for `true'
and the alternative is nil for `false'.
(setq-default case-fold-search nil)
This sets the default value, which is effective in all buffers that do
not have local values for the variable (see Locals). Setting
case-fold-search with setq affects only the current
buffer's local value, which is probably not what you want to do in an
init file.
(setq user-mail-address "cheney@torture.gov")
Various Emacs packages, such as Message mode, consult
user-mail-address when they need to know your email address.
See Mail Headers.
(setq-default major-mode 'text-mode)
Note that text-mode is used because it is the command for
entering Text mode. The single-quote before it makes the symbol a
constant; otherwise, text-mode would be treated as a variable
name.
(set-language-environment "Latin-1")
(line-number-mode 0)
(add-hook 'text-mode-hook
'(lambda () (auto-fill-mode 1)))
This shows how to add a hook function to a normal hook variable
(see Hooks). The function we supply is a list starting with
lambda, with a single-quote in front of it to make it a list
constant rather than an expression.
It's beyond the scope of this manual to explain Lisp functions, but for
this example it is enough to know that the effect is to execute
(auto-fill-mode 1) when Text mode is entered. You can replace
that with any other expression that you like, or with several
expressions in a row.
Emacs comes with a function named turn-on-auto-fill whose
definition is (lambda () (auto-fill-mode 1)). Thus, a simpler
way to write the above example is as follows:
(add-hook 'text-mode-hook 'turn-on-auto-fill)
(load "foo")
When the argument to load is a relative file name, not starting
with ‘/’ or ‘~’, load searches the directories in
load-path (see Lisp Libraries).
(load "~/foo.elc")
Here an absolute file name is used, so no searching is done.
myfunction
by loading a Lisp library named mypackage (i.e. a file
mypackage.elc or mypackage.el):
(autoload 'myfunction "mypackage" "Do what I say." t)
Here the string "Do what I say." is the function's
documentation string. You specify it in the autoload
definition so it will be available for help commands even when the
package is not loaded. The last argument, t, indicates that
this function is interactive; that is, it can be invoked interactively
by typing M-x myfunction <RET> or by binding it to a key.
If the function is not interactive, omit the t or use
nil.
make-symbolic-link
(see Init Rebinding).
(global-set-key "\C-xl" 'make-symbolic-link)
or
(define-key global-map "\C-xl" 'make-symbolic-link)
Note once again the single-quote used to refer to the symbol
make-symbolic-link instead of its value as a variable.
(define-key lisp-mode-map "\C-xl" 'make-symbolic-link)
next-line in Fundamental mode
so that they run forward-line instead.
(substitute-key-definition 'next-line 'forward-line
global-map)
(global-unset-key "\C-x\C-v")
One reason to undefine a key is so that you can make it a prefix. Simply defining C-x C-v anything will make C-x C-v a prefix, but C-x C-v must first be freed of its usual non-prefix definition.
(modify-syntax-entry ?\$ "." text-mode-syntax-table)
narrow-to-region without confirmation.
(put 'narrow-to-region 'disabled nil)
Users typically want Emacs to behave the same on all systems, so the same init file is right for all platforms. However, sometimes it happens that a function you use for customizing Emacs is not available on some platforms or in older Emacs versions. To deal with that situation, put the customization inside a conditional that tests whether the function or facility is available, like this:
(if (fboundp 'blink-cursor-mode)
(blink-cursor-mode 0))
(if (boundp 'coding-category-utf-8)
(set-coding-priority '(coding-category-utf-8)))
You can also simply disregard the errors that occur if the function is not defined.
(condition case ()
(set-face-background 'region "grey75")
(error nil))
A setq on a variable which does not exist is generally
harmless, so those do not need a conditional.