GNU Emacs

https://www.gnu.org/software/emacs/manual/html_node/emacs/
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### Install package with manual specification using package-vc-install

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Fetching-Package-Sources.html

When the first argument is a package specification, you can install from a custom repository. This example specifies the URL, lisp directory, and documentation file for BBDB.

```emacs-lisp
;; Specifying information manually:
(package-vc-install
  '(bbdb :url "https://git.savannah.nongnu.org/git/bbdb.git"
         :lisp-dir "lisp"
         :doc "doc/bbdb.texi"))
```

--------------------------------

### Install package from archive specification with package-vc-install

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Fetching-Package-Sources.html

When the first argument to package-vc-install is a symbol naming a package, Emacs downloads the package's specification from the archive. This example installs BBDB from GNU ELPA.

```emacs-lisp
;; Emacs will download BBDB's specification from GNU ELPA:
(package-vc-install 'bbdb)
```

--------------------------------

### Example outline with heading and body lines

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Outline-Format.html

Shows a sample outline with heading lines starting with asterisks and body lines following. The number of asterisks determines the heading depth.

```plaintext
* Food
This is the body,
which says something about the topic of food.

** Delicious Food
This is the body of the second-level header.

** Distasteful Food
This could have
a body too, with
several lines.

*** Dormitory Food

* Shelter
Another first-level topic with its header line.

```

--------------------------------

### Generate MIME database with update-mime-info

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Android-Software.html

Commands to create a temporary directory, copy the default freedesktop.org MIME catalog, and run update-mime-info to generate the MIME database. Notices about the database not being in the search path are harmless.

```shell
$ mkdir -p my-mime-database/packages
$ cp /usr/share/mime/packages/freedesktop.org.xml my-mime-database/packages
$ update-mime-info my-mime-database

```

--------------------------------

### Diary entry for linewise export

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Diary-iCalendar-Export.html

Example diary entry that, when `diary-icalendar-export-linewise` is set to non-nil, is exported as four separate events on the same day with different start times. The second event has no start time.

```plaintext
2025-05-03
  9AM Lab meeting
    Günter to present on new assay
  Start experiment A
  12:30-1:30PM Lunch with Phil
  16:00 Experiment A finishes; move to freezer

```

--------------------------------

### Add shortdoc examples to C-h f help buffers

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Name-Help.html

Add this hook to your initialization file to make C-h f help buffers include examples of function usage. Requires the shortdoc package.

```emacs-lisp
(add-hook 'help-fns-describe-function-functions
          #'shortdoc-help-fns-examples-function)

```

--------------------------------

### uuencode each file using backquoted ? notation

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Shell-Commands-in-Dired.html

Equivalent to the shell loop example, but uses Dired's `?` substitution to run the command once per file, replacing each `?` with the current file name. The backquoted `?` is also substituted.

```shell
uuencode ? ? > `?`.uu

```

--------------------------------

### C-h x auto-fill-mode RET

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Name-Help.html

Invoke describe-command to display documentation for the named command. The example shows how to get documentation for auto-fill-mode, which is not bound to any key.

```text
C-h x auto-fill-mode `RET`

```

--------------------------------

### Bind C-c h to the string 'hello' using key-description

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Init-Rebinding.html

Uses the convenience function key-description to convert the string 'hello' into the appropriate key sequence syntax, avoiding the cumbersome manual spacing.

```emacs-lisp
(keymap-global-set "C-c h" (key-description "hello"))

```

--------------------------------

### package-vc-install

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Fetching-Package-Sources.html

Installs a package directly from its source repository. The first argument can be a package symbol or a package specification. When given a symbol, Emacs uses the specification from the package archive. When given a specification, it can install from any location.

```APIDOC
## package-vc-install

### Description
Installs a package directly from its source repository. The first argument can be a package symbol or a package specification. When given a symbol, Emacs uses the specification from the package archive. When given a specification, it can install from any location.

### Method
Command

### Arguments
- **package** (symbol or package specification) - Required - The package to install. If a symbol, the specification is downloaded from the package archive. If a list of the form `(name . spec)`, it is used as the package specification.

### Package Specification Keys
- **:url** (string) - Optional - URL of the repository from which to fetch the package's source code.
- **:branch** (string) - Optional - Revision of the code to install. Not the package version number.
- **:lisp-dir** (string) - Optional - Repository-relative directory for loading Lisp sources. Defaults to the repository root.
- **:main-file** (string) - Optional - Main file of the project for gathering package metadata. Defaults to the package name with ".el" appended.
- **:doc** (string) - Optional - Repository-relative documentation file for building an Info file. Can be Texinfo or Org.
- **:make** (string or list of strings) - Optional - Makefile targets to run before building the Info file. Only effective when `package-vc-allow-build-commands` is non-nil.
- **:shell-command** (string) - Optional - Shell command to run before building the Info file. Only effective when `package-vc-allow-build-commands` is non-nil.
- **:vc-backend** (symbol) - Optional - VC backend to use for downloading the repository. If omitted, Emacs guesses from the URL or falls back to `package-vc-default-backend`.

### Examples
```elisp
;; Install using archive specification
(package-vc-install 'bbdb)

;; Install using manual specification
(package-vc-install
  '(bbdb :url "https://git.savannah.nongnu.org/git/bbdb.git"
         :lisp-dir "lisp"
         :doc "doc/bbdb.texi"))
```

### Notes
- Automatically byte-compiles and auto-loads files.
- Installed packages behave like regular packages and can be upgraded or deleted.
- Built-in packages cannot be upgraded using this command.
```

--------------------------------

### systemd socket unit for Emacs server

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Emacs-Server.html

Example ~/.config/systemd/user/emacs.socket file for socket activation. The ListenStream path is where Emacs listens for emacsclient connections; the emacs.service file must also be installed.

```ini
[Socket]
ListenStream=/path/to/.emacs.socket
DirectoryMode=0700

[Install]
WantedBy=sockets.target

```

--------------------------------

### Example buffer list output from list-buffers

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/List-Buffers.html

Example output of the *Buffer List* buffer after typing C-x C-b. The first column shows flags: '.' for the current buffer, '%' for read-only, and '*' for modified. The columns are Buffer, Size, Mode, and File.

```text
CRM Buffer                Size  Mode              File
. * .emacs                3294  Elisp/l           ~/.emacs
 %  *Help*                 101  Help
    search.c             86055  C                 ~/cvs/emacs/src/search.c
 %  src                  20959  Dired by name     ~/cvs/emacs/src/
  * *mail*                  42  Mail
 %  HELLO                 1607  Fundamental       ~/cvs/emacs/etc/HELLO
 %  NEWS                481184  Outline           ~/cvs/emacs/etc/NEWS
    *scratch*              191  Lisp Interaction
  * *Messages*            1554  Messages
```

--------------------------------

### Example regex file emacs.tags

Source: https://www.gnu.org/software/emacs/manual/html_node/emacs/Etags-Regexps.html

Contents of a regex file for etags. Lines beginning with whitespace are ignored, and lines starting with '--' are comments. This file defines a regex for C DEFVAR macros.

```text
        -- This is for GNU Emacs C source files
{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/\1/

```
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