我正在处理一个自定义 .emacs 文件，我将能够在多台不同的计算机上使用该文件。如果系统上存在模式，我希望能够加载它。如果它不存在，我希望 Emacs 停止显示错误：File error: Cannot open load file, X.
例如：
(require 'darkroom-mode)
结果是：
File error: Cannot open load file, darkroom-mode
我file-exists-p用来测试是否存在某些其他文件，但对于这个测试，我假设我需要搜索我的加载路径。我是 Lisp 的新手，所以这让我很困惑。
如果您只想require避免发出错误，可以执行以下操作：
; third arg non-nil means to not signal an error if file not found
; a symbol provides documentation at the invocation (and is non-nil)
(require 'darkroom-mode nil 'noerror)
从文档（C-h f require RET）：
require is a built-in function in `C source code'.
(require feature &optional filename noerror)
If feature feature is not loaded, load it from filename.
If feature is not a member of the list `features', then the feature
is not loaded; so load the file filename.
If filename is omitted, the printname of feature is used as the file name,
and `load' will try to load this name appended with the suffix `.elc' or
`.el', in that order. The name without appended suffix will not be used.
If the optional third argument noerror is non-nil,
then return nil if the file is not found instead of signaling an error.