Eshell is a command shell implemented entirely in Emacs Lisp.
Put the expression below into your ~/.emacs.
;; You can run eshell by M-x eshell
(require 'eshell-auto)
;; Use pcomplete with shell-mode
(require 'pcmpl-auto)
(add-hook 'shell-mode-hook 'pcomplete-shell-setup)
http://emacswiki.org/johnw/eshell.html
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