A summary of Emacs' bundled shell and terminal modes
====================================================
---
date: "2013-04-09"
---

This is based on a post on [reddit][1], published on 2013-04-09.

[1]: http://www.reddit.com/r/emacs/comments/1bzl8b/how_can_i_get_a_dumbersimpler_shell_in_emacs/c9blzyb

Emacs comes bundled with a few different shell and terminal modes.  It
can be hard to keep them straight.  What's the difference between
`M-x term` and `M-x ansi-term`?

Here's a good breakdown of the different bundled shells and terminals
for Emacs, from dumbest to most Emacs-y.

term-mode
---------

Your VT100-esque terminal emulator; it does what most
terminal programs do.  Ncurses-things work OK, but dumping large
amounts of text can be slow.  By default it asks you which shell to
run, defaulting to the environmental variable `$SHELL` (`/bin/bash` for
me).  There are two modes of operation:

* char mode: Keys are sent immediately to the shell (including keys
  that are normally Emacs keystrokes), with the following exceptions:
  * `(term-escape-char) (term-escape-char)` sends `(term-escape-char)`
    to the shell (see above for what the default value is).
  * `(term-escape-char) <anything-else>` is like doing equates to `C-x
    <anything-else>` in normal Emacs.
  * `(term-escape-char) C-j` switches to line mode.
* line mode: Editing is done like in a normal Emacs buffer, `<enter>`
  sends the current line to the shell. This is useful for working with
  a program's output.
  * `C-c C-k` switches to char mode.

This mode is activated with

    ; Creates or switches to an existing "*terminal*" buffer.
    ; The default 'term-escape-char' is "C-c"
    M-x term

or

    ; Creates a new "*ansi-term*" or "*ansi-term*<n>" buffer.
    ; The default 'term-escape-char' is "C-c" and "C-x"
    M-x ansi-term

shell-mode
----------

The name is a misnomer; shell-mode is a terminal
emulator, not a shell; it's called that because it is used for running
a shell (bash, zsh, …).  The idea of this mode is to use an external
shell, but make it Emacs-y.  History is not handled by the shell, but
by Emacs; `M-p` and `M-n` access the history, while arrows/`C-p`/`C-n`
move the point (which is is consistent with other Emacs REPL-type
interfaces).  It ignores VT100-type terminal colors, and colorizes
things itself (it inspects words to see if they are directories, in
the case of `ls`).  This has the benefit that it does syntax
highlighting on the currently being typed command.  Ncurses programs
will of course not work.  This mode is activated with:

    M-x shell

eshell-mode
-----------

This is a shell+terminal, entirely written in Emacs
lisp.  (Interestingly, it doesn't set `$SHELL`, so that will be whatever
it was when you launched Emacs).  This won't even be running zsh or
bash, it will be running "esh", part of Emacs.