如何通过指定包名列表来自动安装 Emacs 包？

; list the packages you want
(setq package-list '(package1 package2))

; list the repositories containing them
(setq package-archives '(("elpa" . "http://tromey.com/elpa/")
                         ("gnu" . "http://elpa.gnu.org/packages/")
                         ("marmalade" . "http://marmalade-repo.org/packages/")))

; activate all the packages (in particular autoloads)
(package-initialize)

; fetch the list of packages available 
(unless package-archive-contents
  (package-refresh-contents))

; install the missing packages
(dolist (package package-list)
  (unless (package-installed-p package)
    (package-install package)))

根据 Profpatsch 的评论和以下答案：

(defun ensure-package-installed (&rest packages)
  "Assure every package is installed, ask for installation if it’s not.

Return a list of installed packages or nil for every skipped package."
  (mapcar
   (lambda (package)
     ;; (package-installed-p 'evil)
     (if (package-installed-p package)
         nil
       (if (y-or-n-p (format "Package %s is missing. Install it? " package))
           (package-install package)
         package)))
   packages))

;; make sure to have downloaded archive description.
;; Or use package-archive-contents as suggested by Nicolas Dudebout
(or (file-exists-p package-user-dir)
    (package-refresh-contents))

(ensure-package-installed 'iedit 'magit) ;  --> (nil nil) if iedit and magit are already installed

;; activate installed packages
(package-initialize)

Emacs 25.1+ 将自动在可定制的 package-selected-packages 变量中跟踪用户安装的包。 package-install 将更新自定义变量，您可以使用 package-install-selected-packages 函数安装所有选定的软件包。

这种方法的另一个方便的优点是您可以使用 package-autoremove 自动删除 package-selected-packages 中未包含的包（尽管它会保留依赖项）。

(package-initialize)
(unless package-archive-contents
  (package-refresh-contents))
(package-install-selected-packages)

来源：http://endlessparentheses.com/new-in-package-el-in-emacs-25-1-user-selected-packages.html

这是我用于 Emacs Prelude 的代码：

(require 'package)
(require 'melpa)
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/") t)
(package-initialize)

(setq url-http-attempt-keepalives nil)

(defvar prelude-packages
  '(ack-and-a-half auctex clojure-mode coffee-mode deft expand-region
                   gist haml-mode haskell-mode helm helm-projectile inf-ruby
                   magit magithub markdown-mode paredit projectile
                   python sass-mode rainbow-mode scss-mode solarized-theme
                   volatile-highlights yaml-mode yari yasnippet zenburn-theme)
  "A list of packages to ensure are installed at launch.")

(defun prelude-packages-installed-p ()
  (loop for p in prelude-packages
        when (not (package-installed-p p)) do (return nil)
        finally (return t)))

(unless (prelude-packages-installed-p)
  ;; check for new packages (package versions)
  (message "%s" "Emacs Prelude is now refreshing its package database...")
  (package-refresh-contents)
  (message "%s" " done.")
  ;; install the missing packages
  (dolist (p prelude-packages)
    (when (not (package-installed-p p))
      (package-install p))))

(provide 'prelude-packages)

如果您不使用 MELPA，则不需要它（如果您这样做，melpa.el 必须在您的 load-path 上（或通过 MELPA 安装）。包 db 不会每次都刷新（因为这会显着减慢启动速度）-仅在存在已卸载软件包的情况下。

还没有人提到 Cask，但它非常适合这项任务。

基本上，您创建 ~/.emacs.d/Cask 列出您要安装的软件包。例如：

(source melpa)
(depends-on "expand-region")
(depends-on "goto-last-change")
; ... etc

从命令行运行 cask 将为您安装这些软件包以及它们所需的任何依赖项。

此外，您可以使用 cask update 自动更新已安装的软件包。

使用包名称作为符号调用 package-install。您可以通过交互调用 package-install 并填写名称来查找您的包裹的包裹名称。函数 package-installed-p 将让您知道它是否已安装。

例如：

(mapc
 (lambda (package)
   (or (package-installed-p package)
       (package-install package)))
 '(package1 package2 package3))

(require 'cl)
(require 'package)

(setq cfg-var:packages '(
       emmet-mode
       ergoemacs-mode
       flycheck
       flycheck-pyflakes
       monokai-theme
       py-autopep8
       py-isort
       rainbow-mode
       yafolding
       yasnippet))

(defun cfg:install-packages ()
    (let ((pkgs (remove-if #'package-installed-p cfg-var:packages)))
        (when pkgs
            (message "%s" "Emacs refresh packages database...")
            (package-refresh-contents)
            (message "%s" " done.")
            (dolist (p cfg-var:packages)
                (package-install p)))))

(add-to-list 'package-archives '("gnu" . "http://elpa.gnu.org/packages/") t)
(add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/") t)
(add-to-list 'package-archives '("melpa-stable" . "http://stable.melpa.org/packages/") t)
(add-to-list 'package-archives '("org" . "http://orgmode.org/elpa/") t)
(package-initialize)

(cfg:install-packages)

我喜欢检查用户是否想先安装软件包，就像在 this answer 中所做的那样。此外，在安装任何东西之前，我都会刷新一次我的包内容。我不确定这是否是最好的方法，但我认为最佳答案并不是为我做的。

(setq required-pkgs '(jedi flycheck cider clojure-mode paredit markdown-mode jsx-mode company))

(require 'cl)

(setq pkgs-to-install
      (let ((uninstalled-pkgs (remove-if 'package-installed-p required-pkgs)))
        (remove-if-not '(lambda (pkg) (y-or-n-p (format "Package %s is missing. Install it? " pkg))) uninstalled-pkgs)))

(when (> (length pkgs-to-install) 0)
  (package-refresh-contents)
  (dolist (pkg pkgs-to-install)
    (package-install pkg)))

这是我的，它更短:)

(mapc
 (lambda (package)
   (unless (package-installed-p package)
     (progn (message "installing %s" package)
            (package-refresh-contents)
            (package-install package))))
 '(browse-kill-ring flycheck less-css-mode tabbar org auto-complete undo-tree clojure-mode markdown-mode yasnippet paredit paredit-menu php-mode haml-mode rainbow-mode fontawesome))

在将 (package-install 'org) 添加到 .emacs 后，我遇到了一个问题。我想安装最新版本的 org-mode，而内置的 org-mode 已经很旧了。

我从 Emacs 25.3.1 中挖出了 package-install 的源代码。函数 self 已经检查是否安装了包，如果包已经安装，则拒绝安装它。因此，实际上不需要来自答案 10093312 的检查 (unless (package-installed-p package) ...)。

(defun package-install (pkg &optional dont-select)
  "Install the package PKG.
PKG can be a package-desc or a symbol naming one of the available packages
in an archive in `package-archives'.  Interactively, prompt for its name.

If called interactively or if DONT-SELECT nil, add PKG to
`package-selected-packages'.

If PKG is a package-desc and it is already installed, don't try
to install it but still mark it as selected."
  (interactive
   (progn
     ;; Initialize the package system to get the list of package
     ;; symbols for completion.
     (unless package--initialized
       (package-initialize t))
     (unless package-archive-contents
       (package-refresh-contents))
     (list (intern (completing-read
                    "Install package: "
                    (delq nil
                          (mapcar (lambda (elt)
                                    (unless (package-installed-p (car elt))
                                      (symbol-name (car elt))))
                                  package-archive-contents))
                    nil t))
           nil)))
  (add-hook 'post-command-hook #'package-menu--post-refresh)
  (let ((name (if (package-desc-p pkg)
                  (package-desc-name pkg)
                pkg)))
    (unless (or dont-select (package--user-selected-p name))
      (package--save-selected-packages
       (cons name package-selected-packages)))
    (if-let ((transaction
              (if (package-desc-p pkg)
                  (unless (package-installed-p pkg)
                    (package-compute-transaction (list pkg)
                                                 (package-desc-reqs pkg)))
                (package-compute-transaction () (list (list pkg))))))
        (package-download-transaction transaction)
      (message "`%s' is already installed" name))))

内置 org-mode 也算作已安装，package-install 拒绝安装来自 ELPA 的较新版本。在花了一些时间阅读 package.el 之后，我想出了以下解决方案。

(dolist (package (package-compute-transaction
                  () (list (list 'python '(0 25 1))
                           (list 'org '(20171211)))))
  ;; package-download-transaction may be more suitable here and
  ;; I don't have time to check it
  (package-install package))

它起作用的原因是 package-* 系列函数根据它是符号还是 package-desc 对象来不同地处理参数。您只能通过 package-desc 对象为 package-install 指定版本信息。

这是另一种方式。

;; assure every package is installed
(defun ensure-package-installed (&rest packages)
  (let ((user-required-packages
         (seq-remove
          (lambda (package) (package-installed-p package))
          packages)))
    (when user-required-packages
      (package-refresh-contents)
      (dolist (package user-required-packages)
        (package-install package)))))

;; list of packages to install
(ensure-package-installed
 'try
 'which-key)

靠近尼古拉斯的answer：

如果包 package-1、package-2 和 package-3 不在本地，则安装它们。如果它们存在，Emacs 将立即加载。

(setq package-archives                                      ;
      '(("gnu" . "https://elpa.gnu.org/packages/")          ; declare repositories
        ("melpa" . "https://melpa.org/packages/")))         ;

(require 'package)                                          ; activate packages
(package-initialize)                                        ; initialize package facility

(setq my-packages
      '(package-1
        package-2
        package-3))

(unless package-archive-contents                            ; unless packages are not available locally, dont refresh package archives
  (package-refresh-contents))                               ; refreshing package contents is time-consuming and should be done on demand

(dolist (pkg my-packages)                                   ;
  (unless (package-installed-p pkg)                         ; iterate over packages and install missing ones
    (package-install pkg)))                                 ;

;; other config below