在Lisp中,使用require时避免"无法打开加载文件"

Question

我正在开发一个自定义的.emacs文件,我可以在几台不同的计算机上使用它.我希望能够加载一个模式,如果它存在于系统上.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是对于这个测试我会假设我需要搜索我的加载路径.我是Lisp的新手,所以这让我很难过.

Answer 1

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.