emacs 进阶：了解命令

命令组成

由于emacs本身就是emacs lisp编写的，所以在emacs中一个命令其实就是一个函数。

(defun helm-M-x (_arg &optional command-name)
"Preconfigured `helm' for Emacs commands.
It is `helm' replacement of regular `M-x' `execute-extended-command'.
Unlike regular `M-x' emacs vanilla `execute-extended-command' command,
the prefix args if needed, can be passed AFTER starting `helm-M-x'.
When a prefix arg is passed BEFORE starting `helm-M-x', the first `C-u'
while in `helm-M-x' session will disable it.

You can get help on each command by persistent action."

快捷键	命令	说明
M-!	shell-command	使用系统shell 运行命令并输出到buffer "Shell Command Output"
M-	shell-command-on-region	运行Shell命令并输出到编辑区域
M-x	helm-M-x	运行emacs命令
-	term	打开buffer"terminal",运行终端
-	eshell	创建一个交互式的Elisp shell。

可以通过设置shell-file-name变量的值来改变默认shell

 (setq shell-file-name "/bin/bash")

eshell的用法

elisp

快速入门

掌握基本语法规则后就应该多看人家写的代码！
利用edebug更好更快地理解代码
假如想要知道打开文件是怎么操作的。

1. 首先定位函数的代码。

   • 已知快捷键C-x C-f。依次键入C-h k C-x C-f。
     然后就会显示函数的信息，点击helm-files.el就能看到代码。

   • 如果不知道快捷键，则键入C-h a ，利用命令的名称来搜索可能的选项。

   (defun helm-find-files (arg)
     "Preconfigured `helm' for helm implementation of `find-file'.
   Called with a prefix arg show history if some.
   Don't call it from programs, use `helm-find-files-1' instead.
   This is the starting point for nearly all actions you can do on files."
     (interactive "P")
     (let* ((hist            (and arg helm-ff-history (helm-find-files-history)))
            (smart-input     (or hist (helm-find-files-initial-input)))
            (default-input   (expand-file-name (helm-current-directory)))
            (input           (cond (helm-find-file-ignore-thing-at-point
                                    default-input)
                                   ((and (eq major-mode 'org-agenda-mode)
                                         org-directory
                                         (not smart-input))
                                    (expand-file-name org-directory))
                                   ((and (eq major-mode 'dired-mode) smart-input)
                                    (file-name-directory smart-input))
                                   ((and (not (string= smart-input ""))
                                         smart-input))
                                   (t default-input)))
            (input-as-presel (null (nth 0 (file-attributes input))))
            (presel          (helm-aif (or hist
                                           (and input-as-presel input)
                                           (buffer-file-name (current-buffer))
                                           (and (eq major-mode 'dired-mode)
                                                smart-input))
                                 (if helm-ff-transformer-show-only-basename
                                     (helm-basename it) it))))
       (set-text-properties 0 (length input) nil input)
       (helm-find-files-1 input (and presel (null helm-ff-no-preselect)
                                     (concat "^" (regexp-quote presel))))))

2. 将光标放到函数名上，键入 C-u C-M-x可添加中断入口。M-x edebug-mod开启后会在菜单栏多出edebug的选项。

3. 使用命令C-x C-f便会触发中断。

4. n可单步执行

IELM

这是一个很方便的工具。不同于M-x只能调用命令，IELM可以使用lisp语言，对于实现emacs扩展实在是太便捷了！

更多更详细的内容还是得看文档！！