emacs self-documentation commands

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There are many emacs commands that tell you about emacs, most of which use the C-h (for "help") prefix.

Table of contents

1. emacs self-documentation commands
   1. Table of contents
   2. Summary of self-help commands
   3. C-h i: The info documentation browser
   4. C-h m Describe the current editing modes
   5. C-h l: view "lossage"
   6. C-h f and C-h C-f: Document a command or function by name
   7. C-h c, C-h k, and C-h C-k: Document a command by keystrokes
   8. C-h a: Apropos commands

General documentation:
• C-h a (command-apropos ) -- prompts for a substring (actually, a regular expression), and shows a list of matching commands (a subset of functions).
• C-h b (describe-bindings) -- displays a table of all key bindings currently in effect.
• prefix C-h displays a table of all key bindings that start with prefix, e.g. "C-x ?" gives you a list of all commands that start with C-x.
• C-h i (info) -- enter the info documentation reader.
• C-h l (view-lossage) -- shows the last hundred characters you typed.
• C-h p (finder-by-keyword) -- Find packages matching a given topic keyword.
• C-h t (help-with-tutorial) -- starts the emacs learn-by-doing tutorial. The tutorial is a file that gives you step-by-step instructions on how to edit it.

  Specific documentation:
  These are designed to produce more detailed documentation for specific items, e.g. commands.

• C-h c (describe-key-briefly) -- prompts for a command key sequence, and displays the command (function) name.
• C-h k (describe-key) -- prompts for a command key sequence, and displays the full command (function) documentation.
• C-h C-k (Info-goto-emacs-key-command-node) -- prompts for a command key sequence, and takes you to the info documentation node for the command bound to that key.
• C-h f (describe-function) -- Type a function name and get documentation of it.
• C-h C-f (Info-goto-emacs-command-node) -- prompts for a function name, and takes you to the info node for that command.
• C-h v (describe-variable) -- prompts for the name of a variable, and displays the variable's documentation and value.
• C-h w (where-is) -- prompts for a command name, and shows which keystrokes invoke that command.

  Mode documentation:

• C-h m (describe-mode) -- views documentation for the current major mode, describing the commands peculiar to it.
• C-h s (describe-syntax) -- displays the contents of the current mode's syntax table, plus explanations of what the codes mean.

  Other information:

• C-h F (view-emacs-FAQ) -- Shows emacs frequently asked questions file.
• C-h n (view-emacs-news; also on C-h C-n) -- shows the emacs "news" file (the change history that came as part of the emacs installation).
• C-h C-c (describe-copying) -- shows Emacs copying permission (the General Public License or GPL).
• C-h C-d (describe-distribution) -- shows Emacs ordering information.
• C-h C-p (describe-project) -- shows information about the GNU project ("The GNU Manifesto").
• C-h C-w (describe-no-warranty) -- shows information on the absence of a warranty for GNU Emacs.

There are only a handful of info commands that are really essential to learn (a tutorial is available, but hardly necessary). An info document is a hierarchy of "nodes"; the browser shows you one node at a time, and the commands are primarily for navigating within and between nodes. Here are the basics:

• mouse-2 -- follows the node reference (menu item, cross reference, etc.) clicked on.
• SPC -- scrolls forward to the next screenful, or, if at the bottom, moves to the next node.
• n -- moves to the next node.
• DEL -- scrolls backward to the previous screenful, or, if at the top of the node, moves to the previous node.
• p -- moves to the previous node.
• u -- moves up to this node's parent.
• m -- prompts for a menu item (with completion), and goes to that node.
• . -- go to the top of the current node.
• q -- exit info by burying the buffer; typing C-h i later on will bring back the buffer where you left off.

One weak point of info is that the manuals tend to be fairly linear (i.e. not hypertextual), a consequence of being produced from the same markup source as the printed manuals. But this is greatly relieved by being easily searchable. It is common for the top-level "node" for a manual to reference first what would be the chapters of the printed edition, and then include a "detailed" listing that includes all of the third-level nodes (sections) within the chapters. This makes it easy to use C-s to find the section of interest, then use m to move into that section. This turns out to be faster than using a paper index, especially for the emacs manuals, which are more than 500 pages each in hardcopy.

Tip: The GNU Emacs Manual and the GNU Emacs Lisp Reference Manual are available on the Web as well; see the "Other resources for more advanced emacs" section.

C-h m Describe the current editing modes

    The minor modes are described first,
    followed by the major mode, which is described on the last page.
    ^L
    auto-fill-function minor mode (indicator Fill):
    Automatically break line at a previous space, in insertion of text.
    ^L
    HTML helper mode:
    Mode for editing HTML documents.
    For more documentation and the newest version, 
    see http://www.santafe.edu/~nelson/tools/

    The main function html-helper-mode provides is a menu and keybindings
    for the HTML tags one inserts when writing HTML documents. Selecting
    the menu item or typing the key sequence for a command inserts the
    corresponding tag and places point in the right place. If a prefix
    argument is supplied, the tags is instead wrapped around the region.
    Alternately, one can type in part of the tag and complete it with M-TAB.

    There is also code for indentation, timestamps, skeletons for new
    documents, and lots of other neat features.

    key             binding
    ---             -------

    RET		newline-and-indent
    TAB		html-helper-indent-command
    ESC		Prefix Command
    C-c		Prefix Command

    . . .

The commands described in the previous section (C-h f and C-h C-f) do the same thing given the command or function name. Taken together, these commands are indispensible for getting full details of exactly what the command does, including special cases, and how it uses the numeric argument (if it does).

C-h a: Apropos commands