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")

elisp

掌握基本语法规则后就应该多看人家写的代码！

假如想要知道打开文件是怎么操作的。

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))))))