#+TITLE: Shell layer
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[[file:img/shell.png]]

* Table of Contents                                         :TOC_4_org:noexport:
 - [[Description][Description]]
 - [[Install][Install]]
   - [[Layer][Layer]]
   - [[Default shell][Default shell]]
   - [[Default shell position and height][Default shell position and height]]
   - [[Set shell for term and ansi-term][Set shell for term and ansi-term]]
   - [[Enable em-smart in Eshell][Enable em-smart in Eshell]]
   - [[Protect your Eshell prompt][Protect your Eshell prompt]]
 - [[Eshell][Eshell]]
 - [[Key bindings][Key bindings]]
   - [[Multi-term][Multi-term]]
   - [[Eshell][Eshell]]

* Description
This layer configures the various shells available in Emacs.

* Install
** Layer
To use this configuration layer, add it to your =~/.spacemacs=. You will need to
add =shell= to the existing =dotspacemacs-configuration-layers= list in this
file.

** Default shell
Emacs supports three types of shell:
- the Emacs shell
- the inferior shell
- the terminal emulator
- the ANSI terminal emulator

You can find a quick introductions to them [[https://www.masteringemacs.org/article/running-shells-in-emacs-overview][here]].

To define the default shell you can set the layer variable =shell-default-shell=
to the following variables:
- =eshell=
- =shell=
- =term=
- =ansi-term=
- =multi-term=

#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers
  '(shell :variables shell-default-shell 'eshell))
#+END_SRC

The default shell is quickly accessible via a the default shortcut key ~SPC '~.

** Default shell position and height
It is possible to choose where the shell should pop up by setting the variable
=shell-default-position= to either =top=, =bottom= or =full=. It is not possible
to show it on the side for now. Default value is =bottom=. It is also possible
to set the default height in percents with the variable =shell-default-height=.
Default value is =30=.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
    '(shell :variables
            shell-default-position 'bottom
            shell-default-height 30))
#+END_SRC

** Set shell for term and ansi-term
The default shell can be set by setting the variable =shell-default-term-shell=.
Default value is =/bin/bash=.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
    '(shell :variables shell-default-term-shell "/bin/bash"))
#+END_SRC

** Enable em-smart in Eshell
From the =em-smart= documentation:

#+BEGIN_QUOTE
The best way to get a sense of what this code is trying to do is by
using it.  Basically, the philosophy represents a blend between the
ease of use of modern day shells, and the review-before-you-proceed
mentality of Plan 9's 9term.
#+END_QUOTE

In a nutshell, when =em-smart= is enabled point won't jump at the end of the
buffer when a command is executed, it will stay at the same command prompt used
to execute the command. This allows to quickly edit the last command in the case
of a mistake. If there is no mistake and you directly type a new command then
the prompt will jump to the next prompt at the end of the buffer.

To enable =em-smart= put the following layer variable to non-nil:

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
    '(shell :variables shell-enable-smart-eshell t))
#+END_SRC

** Protect your Eshell prompt
Comint mode (Shell mode) has good support for Evil mode as it inhibits movement
commands over the prompt. This has the added benefit that Evil mode functions
work sensibly. E.g. you can press ~cc~ in normal state i.e.
=evil-change-whole-line= to kill the current input and start typing a new
command. In Eshell you also kill the prompt, which is often unintended.

By default this layer also protects the =ehsell= prompt. If you want to
disable this protection you can set the variable =shell-protect-eshell-prompt=
to nil.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
    '(shell :variables shell-protect-eshell-prompt nil))
#+END_SRC

* Eshell
Some advanced configuration is setup for =eshell= in this layer:
- some elisp functions aliases for quick access
  - =s= for =magit-status= in the current directory (when the =git= layer is
    installed)
  - =d= for =dired=
  - =e= to find a file via a new buffer
  - =z= for quickly jumping to a previously visited directory
- optional configuration for =em-smart= (see =Install= section for more info)
- support for visual commands via =em-term=
- working directory sensitive prompt via [[https://github.com/hiddenlotus/eshell-prompt-extras][eshell-prompt-extras]]
- advanced help support via =esh-help= (enable =el-doc= support in eshell)
- add support for auto-completion via =company= (when the =auto-completion=
  layer is installed)
- pressing ~i~ in normal state will automatically jump to the prompt

* Key bindings

| Key Binding | Description                                                |
|-------------+------------------------------------------------------------|
| ~SPC '~     | Open, close or go to the default shell                     |
| ~SPC p '~   | Open a shell in the project's root                         |
| ~SPC a s e~ | Open, close or go to an =eshell=                           |
| ~SPC a s i~ | Open, close or go to a =shell=                             |
| ~SPC a s m~ | Open, close or go to a =multi-term=                        |
| ~SPC a s t~ | Open, close or go to a =ansi-term=                         |
| ~SPC a s T~ | Open, close or go to a =term=                              |
| ~SPC m H~   | browse history with =helm= (works in =eshell= and =shell=) |
| ~C-j~       | next item in history                                       |
| ~C-k~       | previous item in history                                   |

*Note:* You can open multiple shells using a numerical prefix argument,
for instance pressing ~2 SPC '~ will a second default shell, the
number of shell is indicated on the mode-line.

** Multi-term

| Key Binding | Description                  |
|-------------+------------------------------|
| ~SPC m c~   | create a new multi-term      |
| ~SPC m n~   | go to next multi-term        |
| ~SPC m p~   | go to previous multi-term    |
| ~SPC p $ t~ | run multi-term shell in root |

** Eshell

| Key Binding        | Description                                |
|--------------------+--------------------------------------------|
| ~SPC m H~ or ~M-l~ | shell commands history using a helm buffer |