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## 46 Saving Emacs Sessions

Use the desktop library to save the state of Emacs from one session to another. Once you save the Emacs desktop—the buffers, their file names, major modes, buffer positions, and so on—then subsequent Emacs sessions reload the saved desktop. By default, the desktop also tries to save the frame and window configuration. To disable this, set `desktop-restore-frames` to `nil`. (See that variable’s documentation for some related options that you can customize to fine-tune this behavior.)

When the desktop restores the frame and window configuration, it uses the recorded values of frame parameters, disregarding any settings for those parameters you have in your init file (see Init File). This means that frame parameters such as fonts and faces for the restored frames will come from the desktop file, where they were saved when you exited your previous Emacs session; any settings for those parameters in your init file will be ignored. To disable this, customize the value of `frameset-filter-alist` to filter out the frame parameters you don’t want to be restored.

You can save the desktop manually with the command `M-x desktop-save`. You can also enable automatic saving of the desktop when you exit Emacs, and automatic restoration of the last saved desktop when Emacs starts: use the Customization buffer (see Easy Customization) to set `desktop-save-mode` to `t` for future sessions, or add this line in your init file (see Init File):

    (desktop-save-mode 1)

When `desktop-save-mode` is active and the desktop file exists, Emacs auto-saves it every `desktop-auto-save-timeout` seconds, if that is non-`nil` and non-zero.

If you turn on `desktop-save-mode` in your init file, then when Emacs starts, it looks for a saved desktop in the current directory. (More precisely, it looks in the directories specified by desktop-path, and uses the first desktop it finds.) Thus, you can have separate saved desktops in different directories, and the starting directory determines which one Emacs reloads. You can save the current desktop and reload one saved in another directory by typing `M-x desktop-change-dir`. Typing `M-x desktop-revert` reverts to the desktop previously reloaded.

Specify the option ‘`--no-desktop`’ on the command line when you don’t want it to reload any saved desktop. This turns off `desktop-save-mode` for the current session. Starting Emacs with the ‘`--no-init-file`’ option also disables desktop reloading, since it bypasses the init file, where `desktop-save-mode` is usually turned on.

By default, all the buffers in the desktop are restored at one go. However, this may be slow if there are a lot of buffers in the desktop. You can specify the maximum number of buffers to restore immediately with the variable `desktop-restore-eager`; the remaining buffers are restored lazily, when Emacs is idle.

Type `M-x desktop-clear` to empty the Emacs desktop. This kills all buffers except for internal ones, and clears the global variables listed in `desktop-globals-to-clear`. If you want this to preserve certain buffers, customize the variable `desktop-clear-preserve-buffers-regexp`, whose value is a regular expression matching the names of buffers not to kill.

If you want to save minibuffer history from one session to another, use the `savehist` library.

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