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Help by Command or Variable Name
`C-h f' (`describe-function') reads the name of a Lisp function
using the minibuffer, then displays that function's documentation string
in a window. Since commands are Lisp functions, you can use this to get
the documentation of a command that is known by name. For example,
C-h f auto-fill-mode RET
displays the documentation of `auto-fill-mode'. This is the only way
to get the documentation of a command that is not bound to any key (one
which you would normally run using `M-x').
`C-h f' is also useful for Lisp functions that you are planning to
use in a Lisp program. For example, if you have just written the
expression `(make-vector len)' and want to check that you are using
`make-vector' properly, type `C-h f make-vector RET'. Because `C-h f'
allows all function names, not just command names, you may find that
some of your favorite abbreviations that work in `M-x' don't work in
`C-h f'. An abbreviation may be unique among command names yet fail to
be unique when other function names are allowed.
The function name for `C-h f' to describe has a default which is
used if you type RET leaving the minibuffer empty. The default is the
function called by the innermost Lisp expression in the buffer around
point, *provided* that is a valid, defined Lisp function name. For
example, if point is located following the text `(make-vector (car x)',
the innermost list containing point is the one that starts with
`(make-vector', so the default is to describe the function
`C-h f' is often useful just to verify that you have the right
spelling for the function name. If `C-h f' mentions a default in the
prompt, you have typed the name of a defined Lisp function. If that is
all you want to know, just type `C-g' to cancel the `C-h f' command,
then go on editing.
`C-h w COMMAND RET' tells you what keys are bound to COMMAND. It
prints a list of the keys in the echo area. If it says the command is
not on any key, you must use `M-x' to run it.
`C-h v' (`describe-variable') is like `C-h f' but describes Lisp
variables instead of Lisp functions. Its default is the Lisp symbol
around or before point, but only if that is the name of a known Lisp
variable. Note: Variables.
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