Opening definition of Emacs command

is it possible to open in ema开发者_如何学Ccs elisp file with command definition, to see, how it is defined?

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Yes you can call M-x find-function

Some functions are implemented in C. To be able to find C function you have to download C sources (if you have not yet done so) and add the following line to your .emacs

(setq find-function-C-source-directory "/path/to/c-source")

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Another way:

C-h f foo RET to see the documentation for the function foo.

The documentation will tell you, on the first line, where and how the function is defined. Click the link (or hit RET with cursor on it) to the source file where the command is defined. You have to have the Lisp sources (for Lisp code) or the C sources (for C code) installed on your system in order for this to work.

You can also start from a key, without knowing what its command is: C-h k.