API for shell-mode?

[J Krugman]

Where can I find the API/documentation for the Emacs shell mode
(i.e. the mode of the buffer one gets when one types 'M-x shell').

My immediate question are the specs on the possible values for the
$EMACS environment variable.  Is there any other possible value
other than 't'?

(This is only the latest of several questions I've had over the
years about the shell-mode, but I can never find adequate documentation
for it, other than a list of key bindings.)

Thanks,

jill

-- 
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