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(emacs)Interactive Shell

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Interactive Inferior Shell
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   To run a subshell interactively, putting its typescript in an Emacs
buffer, use `M-x shell'.  This creates (or reuses) a buffer named
`*shell*' and runs a subshell with input coming from and output going
to that buffer.  That is to say, any "terminal output" from the subshell
goes into the buffer, advancing point, and any "terminal input" for the
subshell comes from text in the buffer.  To give input to the subshell,
go to the end of the buffer and type the input, terminated by <RET>.

   Emacs does not wait for the subshell to do anything.  You can switch
windows or buffers and edit them while the shell is waiting, or while
it is running a command.  Output from the subshell waits until Emacs
has time to process it; this happens whenever Emacs is waiting for
keyboard input or for time to elapse.

   Input lines, once you submit them, are displayed using the face
`comint-highlight-input', and prompts are displayed using the face
`comint-highlight-prompt'.  This makes it easier to see previous input
lines in the buffer.  Note: Faces.

   To make multiple subshells, you can invoke `M-x shell' with a prefix
argument (e.g. `C-u M-x shell'), which will read a buffer name and
create (or reuse) a subshell in that buffer.  You can also rename the
`*shell*' buffer using `M-x rename-uniquely', then create a new
`*shell*' buffer using plain `M-x shell'.  All the subshells in
different buffers run independently and in parallel.

   The file name used to load the subshell is the value of the variable
`explicit-shell-file-name', if that is non-`nil'.  Otherwise, the
environment variable `ESHELL' is used, or the environment variable
`SHELL' if there is no `ESHELL'.  If the file name specified is
relative, the directories in the list `exec-path' are searched; this
list is initialized based on the environment variable `PATH' when Emacs
is started.  Your `.emacs' file can override either or both of these
default initializations.

   Emacs sends the new shell the contents of the file
`~/.emacs_SHELLNAME' as input, if it exists, where SHELLNAME is the
name of the file that the shell was loaded from.  For example, if you
use bash, the file sent to it is `~/.emacs_bash'.

   To specify a coding system for the shell, you can use the command
`C-x <RET> c' immediately before `M-x shell'.  You can also specify a
coding system after starting the shell by using `C-x <RET> p' in the
shell buffer.  Note: Specify Coding.

   Unless the environment variable `EMACS' is already defined, Emacs
defines it in the subshell, with value `t'.  A shell script can check
this variable to determine whether it has been run from an Emacs
subshell.