WEBVTT captioned by mark
NOTE Introduction
00:00:02.940 --> 00:00:08.719
Welcome to Emacs as a Shell, a talk by Christopher Howard for
00:00:08.720 --> 00:00:13.799
Emacs Conference 2024.
00:00:13.800 --> 00:00:18.399
In this talk, I would like to explore, or advocate for, a
00:00:18.400 --> 00:00:21.919
particular perspective. I want to encourage people to
00:00:21.920 --> 00:00:26.479
think of Emacs not as simply an editor or a development
00:00:26.480 --> 00:00:31.119
environment, but rather as a shell, or at least something
00:00:31.120 --> 00:00:33.919
that allows us to do most of the things that we might
00:00:33.920 --> 00:00:37.880
otherwise want to do from a shell.
NOTE What do I mean by shell?
00:00:37.881 --> 00:00:40.839
What do I mean by shell? By
00:00:40.840 --> 00:00:45.439
shell, I mean basically an interface that allows us to
00:00:45.440 --> 00:00:50.679
interact with the rest of our system by entering commands.
00:00:50.680 --> 00:00:55.039
That definition is, perhaps, a little too broad, and so I
00:00:55.040 --> 00:00:58.439
will try to narrow it down with a list of features that,
00:00:58.440 --> 00:01:03.279
historically, we have come to expect from a shell. The Bash
00:01:03.280 --> 00:01:07.719
shell is one very portable and well-known shell, and for
00:01:07.720 --> 00:01:13.599
many of us it is maybe the prototypical example. But in the
00:01:13.600 --> 00:01:16.879
past there have been many other shells, and there are other
00:01:16.880 --> 00:01:21.119
shells available today. If we are willing to be flexible in
00:01:21.120 --> 00:01:25.559
our thinking, we can think of Emacs as being a shell, or at
00:01:25.560 --> 00:01:28.879
least providing most of the functionality that we expect
00:01:28.880 --> 00:01:38.559
from a shell.
NOTE What I do not mean
00:01:38.560 --> 00:01:42.759
Before further expanding on this idea, I must emphasize
00:01:42.760 --> 00:01:47.159
what I do not mean. First of all, I am not talking about
00:01:47.160 --> 00:01:51.439
running Bash, or some other external shell, from within
00:01:51.440 --> 00:01:56.439
Emacs, although this is certainly possible. I am arguing,
00:01:56.440 --> 00:02:02.439
rather, for using Emacs as a shell, instead of other shells.
00:02:02.440 --> 00:02:06.239
Second, I do not mean running a terminal emulator from
00:02:06.240 --> 00:02:11.399
within Emacs. Emacs has a built-in terminal emulator, but
00:02:11.400 --> 00:02:15.839
this is not what I mean. A terminal emulator is essentially a
00:02:15.840 --> 00:02:20.039
program designed to control the cursor and text appearance
00:02:20.040 --> 00:02:23.999
in response to various control codes in order to mimic a
00:02:24.000 --> 00:02:28.439
terminal display device. There are certainly legitimate
00:02:28.440 --> 00:02:32.559
reasons to do this. Nevertheless, in general, it does not
00:02:32.560 --> 00:02:36.519
make much sense to run a terminal emulator within Emacs,
00:02:36.520 --> 00:02:39.719
because Emacs has its own commands for controlling the
00:02:39.720 --> 00:02:45.039
cursor and text appearance. Also, due to the way Emacs was
00:02:45.040 --> 00:02:48.919
designed historically, Emacs itself believes that it is
00:02:48.920 --> 00:02:53.119
running on a terminal. So you end up with layers upon layers
00:02:53.120 --> 00:02:58.199
of terminal emulation. Anyhow, at the end of the day, Emacs
00:02:58.200 --> 00:03:01.839
will not perform as well as a dedicated terminal emulator
00:03:01.840 --> 00:03:08.079
program. I also think that, as we try to force ANSI terminal
00:03:08.080 --> 00:03:12.359
emulation into our Emacs workflow, this ultimately will be
00:03:12.360 --> 00:03:15.879
a hindrance to us in taking advantage of the natural and
00:03:15.880 --> 00:03:19.319
pleasant interfaces that are already available to us
00:03:19.320 --> 00:03:24.999
within Emacs. In brief, if your goal is simply to figure out
00:03:25.000 --> 00:03:28.499
how to be able to do all your normal Bash command line
00:03:28.500 --> 00:03:32.359
wizardry from within an Emacs window instead of a GNOME
00:03:32.360 --> 00:03:36.479
console window, you are headed down a different set of train
00:03:36.480 --> 00:03:43.199
tracks than I am. Also, something which I fear may confuse
00:03:43.200 --> 00:03:47.919
the issue for some viewers is the fact that Emacs ships with
00:03:47.920 --> 00:03:52.839
its own unique built-in shell, called the Emacs shell, or
00:03:52.840 --> 00:03:59.079
Eshell.
00:03:59.080 --> 00:04:02.959
Eshell aims to be a legitimate shell, and provides a very
00:04:02.960 --> 00:04:07.599
similar experience to other shells like Bash, while being
00:04:07.600 --> 00:04:11.119
well integrated into the Emacs interface, and without
00:04:11.120 --> 00:04:15.639
giving up the power of the Emacs Lisp engine. Eshell will be
00:04:15.640 --> 00:04:19.139
mentioned multiple times in this talk. The entire talk
00:04:19.140 --> 00:04:24.179
could, in fact, be about Eshell, except that I want the talk
00:04:24.180 --> 00:04:28.319
to cover all aspects of Emacs shell-like functionality
00:04:28.320 --> 00:04:32.079
through its other tools, such as interactive commands and
00:04:32.080 --> 00:04:37.079
special modes. So, hopefully we can keep distinct in our
00:04:37.080 --> 00:04:43.279
mind the ideas of Emacs as a shell versus the Emacs shell,
00:04:43.880 --> 00:04:50.159
though the latter is an important part of the former.
NOTE What is a shell?
00:04:50.160 --> 00:04:55.399
Let's get back to the fundamental idea of what is a shell. In
00:04:55.400 --> 00:04:59.159
the broadest definition, a shell is an interface which
00:04:59.160 --> 00:05:02.279
allows you to interact with your operating system through
00:05:02.280 --> 00:05:06.840
commands. However, from a historical perspective, there
00:05:06.841 --> 00:05:10.699
are a few basic capabilities which we expect to be part of
00:05:10.700 --> 00:05:17.880
every shell.
00:05:17.881 --> 00:05:21.420
First of all, the shell provides a means of launching
00:05:21.421 --> 00:05:26.440
external programs. Some internal or built-in commands
00:05:26.441 --> 00:05:31.679
might also be made available. Second, the shell provides a
00:05:31.680 --> 00:05:36.820
means of managing environment variables. In the past,
00:05:36.821 --> 00:05:40.580
environment variables often played a critical role as a
00:05:40.581 --> 00:05:45.360
means of passing in options, file names, device names, and
00:05:45.361 --> 00:05:50.119
suchlike to external programs. This is not quite as common
00:05:50.120 --> 00:05:54.080
today, but the environment still plays a critical role in
00:05:54.081 --> 00:05:57.619
managing things such as the path to executables and
00:05:57.620 --> 00:06:03.080
libraries, as well as various other user, desktop, and
00:06:03.081 --> 00:06:08.280
system settings. The shell modifies the environment and
00:06:08.281 --> 00:06:11.620
passes it on to external programs.
00:06:13.540 --> 00:06:17.580
Historically, job control was expected to be either a
00:06:17.581 --> 00:06:21.560
function of the shell, or easily accessible from it.
00:06:21.561 --> 00:06:24.019
Usually today, our personal computing is not
00:06:24.020 --> 00:06:29.280
batch-oriented. But typically, shells can run multiple
00:06:29.281 --> 00:06:34.599
processes simultaneously, as well as provide means to
00:06:34.600 --> 00:06:38.780
suspend and terminate processes, which are useful
00:06:38.781 --> 00:06:44.880
features. Shells should be able to redirect and pipeline
00:06:44.881 --> 00:06:49.100
process input and output. This allows the user to connect
00:06:49.101 --> 00:06:53.880
process input and output with files, devices, or other
00:06:53.881 --> 00:06:58.813
processes. Finally, shells are expected to have some
00:06:58.814 --> 00:07:02.380
limited scripting capability, such as the
00:07:02.381 --> 00:07:06.613
POSIX-compliant set of program statements and
00:07:06.614 --> 00:07:08.880
conditionals that Bash provides.
00:07:11.100 --> 00:07:15.113
As command-line wizards, there are a number of tasks we
00:07:15.114 --> 00:07:18.280
expect to be able to do quickly and easily from our shell,
00:07:18.660 --> 00:07:21.646
even though these tasks are not the domain of the shell
00:07:21.647 --> 00:07:27.880
itself. A common task is file management and navigation. We
00:07:27.881 --> 00:07:31.113
quickly navigate and manipulate the file system with
00:07:31.114 --> 00:07:34.813
standard utilities that do things like change the current
00:07:34.814 --> 00:07:39.380
working directory, rename files, move files, and delete
00:07:39.381 --> 00:07:44.146
files. We usually expect to have access to some additional
00:07:44.147 --> 00:07:48.380
process management utilities. These allow us to do things
00:07:48.381 --> 00:07:51.780
such as find out the status of all processes running on the
00:07:51.781 --> 00:07:57.980
system, and send signals to processes. Finally, we expect
00:07:57.981 --> 00:08:02.113
to have access to some basic networking utilities. For
00:08:02.114 --> 00:08:05.413
example, we should be able to run commands that set up
00:08:05.414 --> 00:08:09.513
network interfaces, ping computers, and download files.
00:08:09.514 --> 00:08:16.080
With a little reflection, we can see that Emacs can provide
00:08:16.081 --> 00:08:20.146
all or nearly all of the functionality we have described so
00:08:20.147 --> 00:08:24.046
far. And the functionality can be called conveniently
00:08:24.047 --> 00:08:26.746
through one of several methods.
00:08:33.520 --> 00:08:43.846
Either a normal interactive call, like M-x something, or a
00:08:43.847 --> 00:08:46.013
call to an elisp function,
00:08:53.620 --> 00:09:01.180
or through Eshell commands, or through some special buffer
00:09:01.181 --> 00:09:06.946
mode, such as the directory editor, which provides its own
00:09:06.947 --> 00:09:09.413
interface to some functionality.
00:09:09.414 --> 00:09:17.413
It may be going too far to say that Emacs is a full replacement
00:09:17.414 --> 00:09:21.713
for shells like Bash. Nevertheless, we can see that Emacs
00:09:21.714 --> 00:09:25.680
can do most of the things that we might otherwise do with our
00:09:25.681 --> 00:09:26.911
shell.
NOTE Launching external processes
00:09:26.912 --> 00:09:32.513
Let us give some examples. First, can Emacs launch
00:09:32.514 --> 00:09:36.680
external commands? Of course. Now, there are something
00:09:36.681 --> 00:09:40.446
like a half-dozen different ways to do that within Emacs, and
00:09:40.447 --> 00:09:46.713
some are more convenient than others. From any Elisp
00:09:46.714 --> 00:09:50.780
program, we can call functions like make-process and
00:09:50.781 --> 00:09:53.913
call-process to launch external processes.
00:10:12.460 --> 00:10:16.846
These, however, generally are not convenient for quick,
00:10:16.847 --> 00:10:22.380
one-off commands. Another option would be to run Eshell,
00:10:22.381 --> 00:10:26.580
which would allow us to call the external program from a
00:10:26.581 --> 00:10:28.946
familiar command line prompt.
00:10:34.160 --> 00:10:38.880
If we do not actually want to drop into Eshell just to run one
00:10:38.881 --> 00:10:42.213
command, we also have the interactive command,
00:10:42.214 --> 00:10:44.613
eshell-command,
00:10:52.420 --> 00:10:56.746
which would allow us to call the external program from a
00:10:56.747 --> 00:10:59.180
familiar command line prompt.
00:11:09.940 --> 00:11:12.080
If we do not actually want to drop an
00:11:12.081 --> 00:11:15.699
Eshell just to run one command, as I just mentioned, we also
00:11:15.700 --> 00:11:19.799
have the interactive command eshell-command, which allows
00:11:19.800 --> 00:11:23.399
us to enter in a one-off command and run that immediately.
00:11:25.420 --> 00:11:28.799
And finally, there is also an interactive command called
00:11:28.800 --> 00:11:30.499
simply shell-command.
00:11:34.600 --> 00:11:39.099
Shell command is like Eshell command, but instead passes
00:11:39.100 --> 00:11:42.899
the command off to our system shell, for example, bash.
00:11:43.940 --> 00:11:48.599
This is cheating, of course, but it might be useful or convenient
00:11:48.600 --> 00:11:57.299
in some scenarios.
NOTE Environment variables
00:11:57.300 --> 00:12:01.899
Regarding environment variables, Emacs can read and
00:12:01.900 --> 00:12:05.399
manipulate the environment variables, which in turn get
00:12:05.400 --> 00:12:09.659
passed on to processes which it launches. The
00:12:09.660 --> 00:12:12.899
general-purpose interactive commands for this are
00:12:12.900 --> 00:12:18.499
getenv and setenv. These commands
00:12:18.500 --> 00:12:21.799
deal with the one environment that is available throughout
00:12:21.800 --> 00:12:25.699
all parts of your running Emacs session. In other words,
00:12:25.700 --> 00:12:28.999
these functions deal with a global environment, which is
00:12:29.000 --> 00:12:32.099
the same wherever you are running getenv or
00:12:32.100 --> 00:12:34.399
setenv.
00:13:00.340 --> 00:13:04.259
An important exception is that every instance of Eshell
00:13:04.260 --> 00:13:07.599
maintains a distinct environment that will not be affected
00:13:07.600 --> 00:13:13.980
by setenv calls run in other buffers. Also, Eshell
00:13:13.981 --> 00:13:16.446
has some additional syntax for dealing with its
00:13:16.447 --> 00:13:20.780
environment, including the set and export syntax.
00:13:38.647 --> 00:13:47.113
Regarding job control and process management, Emacs does
00:13:47.114 --> 00:13:50.880
not provide job control in the way that Bash users are used
00:13:50.881 --> 00:13:57.080
to. We can, however, launch asynchronous processes, and do
00:13:57.081 --> 00:14:01.580
various things to them. From Eshell, or an eshell-command
00:14:01.581 --> 00:14:07.180
call, we can append the ampersand symbol to the command, and
00:14:07.181 --> 00:14:11.013
this will cause the process to run asynchronously in a
00:14:11.014 --> 00:14:13.313
dedicated buffer.
00:14:20.881 --> 00:14:25.280
Now, if the command is launched from Eshell, it will not
00:14:25.281 --> 00:14:31.180
actually run in a separate buffer, but the output will go to
00:14:31.181 --> 00:14:33.413
the Eshell buffer.
NOTE Processes
00:14:54.400 --> 00:14:59.580
We can run the interactive command list-processes to see
00:14:59.581 --> 00:15:02.846
all the processes running for our current Emacs session.
00:15:11.747 --> 00:15:17.646
In Eshell, we can run the command "jobs" to get the same list.
00:15:17.647 --> 00:15:22.813
This will show the process name, process buffer name,
00:15:22.814 --> 00:15:28.613
process ID, and some other information. We can select the
00:15:28.614 --> 00:15:32.880
process buffer in the process list to bring up that process
00:15:32.881 --> 00:15:36.213
buffer.
00:15:42.414 --> 00:15:47.046
We can also use the interactive command signal-process to
00:15:47.047 --> 00:15:52.980
send any signal to a process, including "stop" to suspend the
00:15:52.981 --> 00:15:58.380
process, "continue" to resume the process, and "interrupt" or
00:15:58.381 --> 00:16:02.546
kill to terminate the process.
NOTE Redirecting and pipelining input and output
00:17:00.180 --> 00:17:04.813
Regarding redirecting and pipelining input and output,
00:17:04.814 --> 00:17:11.613
Eshell does support redirection similar to Bash, so you can
00:17:11.614 --> 00:17:17.046
overwrite and append to files and some other objects. Input
00:17:17.047 --> 00:17:22.380
redirection is not yet implemented, but it is on the Eshell
00:17:22.381 --> 00:17:29.213
to-do list. Eshell also has pipes. The default pipe, which
00:17:29.214 --> 00:17:33.220
uses the familiar vertical bar symbol, pipes the data
00:17:33.221 --> 00:17:36.980
between the commands using an intermediate Emacs buffer.
00:17:36.981 --> 00:17:41.200
This, while usually quite practical, is less efficient
00:17:41.201 --> 00:17:46.319
than the system pipe. Therefore, Eshell also makes
00:17:46.320 --> 00:17:50.146
available a star-modified version, which uses the system
00:17:50.147 --> 00:17:52.546
pipe through a call to your system shell.
00:17:56.881 --> 00:17:59.413
So we can do things like
00:18:02.340 --> 00:18:05.860
direct output to a file.
00:18:15.100 --> 00:18:20.240
We're unfortunately not able to do input redirection, but
00:18:20.241 --> 00:18:22.540
we can use pipes.
00:18:41.760 --> 00:18:45.639
Elisp can manipulate and tie together processes in various
00:18:45.640 --> 00:18:50.999
ways, such as process filters and pipe processes, but I
00:18:51.000 --> 00:18:56.559
won't attempt to cover that. I feel like you should mention
00:18:56.560 --> 00:19:02.119
again that we have two kinds of pipes here available. So this
00:19:02.120 --> 00:19:09.239
pipe, the standard one, will pipe the data through Emacs
00:19:09.240 --> 00:19:16.759
buffers. That's very practical in most cases, but it is less
00:19:16.760 --> 00:19:22.919
efficient than piping through the system pipe. So Eshell
00:19:22.920 --> 00:19:28.119
makes available another symbol for that, star, vertical
00:19:28.120 --> 00:19:38.339
bar, that allows you to explicitly use the system pipe.
00:19:38.340 --> 00:19:43.599
Regarding scripting: Of course, using Emacs makes
00:19:43.600 --> 00:19:47.959
available all the power of the Elisp API and third-party
00:19:47.960 --> 00:19:54.719
packages, so we have that out of the gate. Eshell also has
00:19:54.720 --> 00:19:59.639
control flow statements, like an "if" construct and a "for"
00:19:59.640 --> 00:20:06.519
construct. See the Eshell info manual, section 3.7, for
00:20:06.520 --> 00:20:07.719
more details.
NOTE Scripts
00:20:09.440 --> 00:20:13.839
And if you wish to write a script entirely in Eshell syntax,
00:20:13.840 --> 00:20:18.559
and store it in a separate file, this is possible with recent
00:20:18.560 --> 00:20:20.159
versions of Emacs.
00:20:31.840 --> 00:20:34.679
Here's an example of a brief script that I wrote.
00:20:37.560 --> 00:20:42.679
Unfortunately, an eshell mode for proper syntax
00:20:42.680 --> 00:20:46.279
highlighting is not yet available, but hopefully that will
00:20:46.280 --> 00:20:51.279
be forthcoming. Note that Eshell syntax allows elisp
00:20:51.280 --> 00:20:55.079
forms to be interspersed with regular command form for
00:20:55.080 --> 00:20:58.759
additional scripting power. We will discuss this a little
00:20:58.760 --> 00:21:01.999
more later.
NOTE File system management
00:21:11.780 --> 00:21:16.759
Regarding file system management. In Emacs, many of the
00:21:16.760 --> 00:21:20.239
common file system operations are available as
00:21:20.240 --> 00:21:26.759
interactive commands. For example, M-x cd, to change your
00:21:26.760 --> 00:21:32.839
buffer's current working directory, and other M-x commands
00:21:32.840 --> 00:21:37.439
such as make-directory
00:21:40.780 --> 00:21:42.679
chmod,
00:21:43.260 --> 00:21:51.159
and delete-file. Of course, you can also drop into Eshell,
00:21:53.840 --> 00:22:00.639
or use M-x eshell-command to run the usual external commands
00:22:00.640 --> 00:22:07.039
for file system manipulation. Also, a file manager is built
00:22:07.040 --> 00:22:14.279
into Emacs, which can be run by calling M-x dired.
00:22:19.640 --> 00:22:24.559
The directory editor is powerful, but it is a bit strange to
00:22:24.560 --> 00:22:28.679
folks expecting something like Midnight Commander or the
00:22:28.680 --> 00:22:35.639
GNOME file manager. It gives us a number of helpful features
00:22:35.640 --> 00:22:43.639
like the ability to mark files, and to run elisp functions on
00:22:44.700 --> 00:22:48.439
them, and some other interesting ways to manipulate and
00:22:48.440 --> 00:22:54.079
rename the files. However, third-party Emacs extensions
00:22:54.080 --> 00:22:58.479
such as Midnight Commander Mode and Sunrise Commander are
00:22:58.480 --> 00:23:03.879
available to provide a Midnight Commander experience, for those who
00:23:03.880 --> 00:23:10.319
prefer that sort of file management.
00:23:10.320 --> 00:23:14.879
Emacs also has the nifty TRAMP functionality built in,
00:23:14.880 --> 00:23:19.159
which allows you, most of the time, to easily edit files on
00:23:19.160 --> 00:23:22.719
other computers, as well as manipulate the file system.
00:23:23.180 --> 00:23:27.839
This transparently works through SSH and some other
00:23:27.840 --> 00:23:30.079
protocols that you can specify.
NOTE Networking
00:23:43.560 --> 00:23:48.159
Regarding networking features, I don't have a lot of
00:23:48.160 --> 00:23:51.639
interesting things to say about this at the present, so I'll
00:23:51.640 --> 00:23:54.919
skip through this quickly. But if you do a little research,
00:23:54.920 --> 00:23:58.799
you will see that Emacs has a lot of functionality relating
00:23:58.800 --> 00:24:02.359
to making network connections, interacting with the web,
00:24:02.780 --> 00:24:07.859
and such like, both built-in and in available packages, as
00:24:07.860 --> 00:24:14.399
well as modes for doing things like Web browsing and Gemini
00:24:14.400 --> 00:24:20.599
browsing. And of course, you can run the usual standard
00:24:20.600 --> 00:24:23.639
networking commands for your system through Eshell.
NOTE A brief tour of Eshell
00:24:30.120 --> 00:24:33.759
So having put forward the main arguments for this talk, I
00:24:33.760 --> 00:24:38.199
would like to take some time now to give a brief tour of a few of
00:24:38.200 --> 00:24:43.799
the features of Eshell, the Emacs shell. It bears
00:24:43.800 --> 00:24:46.999
emphasizing that Eshell is not a drop-in replacement for
00:24:47.000 --> 00:24:51.879
Bash, or even a Bash clone, though I believe the developers
00:24:51.880 --> 00:24:56.839
are trying to make much of the syntax very similar. Also,
00:24:56.840 --> 00:25:00.479
Eshell is not a terminal emulator, and it will not display
00:25:00.480 --> 00:25:04.679
correctly applications which use advanced ANSI control
00:25:04.680 --> 00:25:10.119
codes. However, Eshell can be configured to be aware of such
00:25:10.120 --> 00:25:13.300
applications, and to run them automatically within the
00:25:13.301 --> 00:25:19.940
Emacs terminal emulator when launched. See section 5.1 of
00:25:19.941 --> 00:25:24.100
the Eshell manual titled Visual Commands.
00:25:32.540 --> 00:25:36.759
Though Eshell is not Bash, it has multiple features,
00:25:36.760 --> 00:25:40.679
pertaining mainly to its by-design Emacs integration,
00:25:40.680 --> 00:25:44.639
which may make it more appealing to use than Bash or another
00:25:44.640 --> 00:25:45.359
shell.
00:25:48.160 --> 00:25:52.039
For one, Eshell allows entering commands on the command
00:25:52.040 --> 00:25:55.960
line that are space and new line separated, without
00:25:55.961 --> 00:26:01.280
parentheses. Of course, all the other shells do this. But
00:26:01.281 --> 00:26:06.280
within Eshell, it is possible to enter internal Emacs
00:26:06.281 --> 00:26:11.060
functions, as well as external commands.
00:26:13.240 --> 00:26:45.739
This allows us to do things like this.
00:26:45.740 --> 00:26:49.759
As far as I understand, it is possible to enter any Emacs
00:26:49.760 --> 00:26:53.959
function on the Eshell command line. However, some special
00:26:53.960 --> 00:26:58.399
syntax may be required if you are trying to pass in something
00:26:58.400 --> 00:27:00.799
that is not a string or a number.
00:27:04.380 --> 00:27:07.919
As you might have noticed in the last example, Eshell makes
00:27:07.920 --> 00:27:12.919
it possible to use an Emacs buffer as a sink for output. It
00:27:12.920 --> 00:27:18.039
also allows using a buffer as a source of input, though this
00:27:18.040 --> 00:27:21.839
is slightly more complicated, since the buffer must be
00:27:21.840 --> 00:27:27.199
converted to a string first. I have distilled this down into
00:27:27.200 --> 00:27:30.279
my own function, named with the "at" symbol.
00:27:36.640 --> 00:27:40.319
And I will provide the brief snippet of code for this later.
00:27:54.640 --> 00:28:02.499
So to give an example, here's our messages buffer.
00:28:02.500 --> 00:28:05.399
And from Eshell, we can do something like this.
00:28:29.780 --> 00:28:34.439
Let's say here we wanted to grab our messages buffer to see
00:28:34.440 --> 00:28:38.079
everything that we had been loading during the startup
00:28:38.080 --> 00:28:38.959
process.
00:28:48.060 --> 00:28:51.879
So you can see how that could be very handy in a number of
00:28:51.880 --> 00:28:52.959
scenarios.
00:28:55.060 --> 00:29:00.239
I wanted to briefly mention that we have a helpful function
00:29:00.240 --> 00:29:03.439
here called eshell-insert-buffer-name,
00:29:11.120 --> 00:29:15.359
which allows us to insert a buffer name into the current
00:29:15.360 --> 00:29:18.439
buffer at point using completion,
00:29:24.680 --> 00:29:32.879
which can save you a lot of typing.
00:29:32.880 --> 00:29:34.799
Another nice feature of Eshell
00:29:37.220 --> 00:29:41.199
is that it allows integrating ELisp into the command line
00:29:41.200 --> 00:29:48.879
call. Let's give another example. Say we wanted to echo the
00:29:48.880 --> 00:29:53.919
date to an event file or an event log.
00:29:56.720 --> 00:30:01.639
I should probably take a moment to explain this asterisk
00:30:01.640 --> 00:30:06.999
that I'm occasionally using. So since Emacs, or excuse me,
00:30:07.000 --> 00:30:11.719
since Eshell can use internal or external Emacs, excuse me,
00:30:11.720 --> 00:30:16.999
internal Emacs commands or external commands, it may
00:30:17.000 --> 00:30:21.679
sometimes be necessary to clarify which one you want to use,
00:30:22.380 --> 00:30:27.079
since the names may overlap. Since my Eshell is configured
00:30:27.080 --> 00:30:32.319
by default to prefer the internal Emacs functions, then
00:30:32.320 --> 00:30:37.799
sometimes I have to use the asterisk to specify that I want
00:30:37.800 --> 00:30:39.079
the external version.
00:30:42.680 --> 00:31:02.639
Here I can insert a bit of Elisp,
00:31:03.180 --> 00:31:06.119
and then redirect the output to the event log.
00:31:18.720 --> 00:31:22.639
Last, I want to mention that there are some optional Eshell
00:31:22.640 --> 00:31:27.159
modules in Emacs, not turned on by default, which provide
00:31:27.160 --> 00:31:29.039
additional nifty features.
00:31:40.540 --> 00:31:45.639
On my system, I have most of the optional modules turned on.
00:31:58.320 --> 00:32:03.199
An interesting module is eshell-smart, which does various
00:32:03.200 --> 00:32:07.319
things with cursor positioning and scrolling, so as to make
00:32:07.320 --> 00:32:10.399
editing commands and reviewing output easier.
00:32:18.340 --> 00:32:23.619
Let's say I was to change directory to my boot directory
00:32:30.880 --> 00:32:35.039
and use a command which involves lots of output.
00:32:39.900 --> 00:32:44.359
You'll notice right away that the cursor positioning is set
00:32:44.360 --> 00:32:48.719
such that I'm immediately able to view the top of the output.
00:32:48.720 --> 00:32:52.879
Also, I'm able to use the space bar to page through the
00:32:52.880 --> 00:32:56.079
output.
00:32:56.080 --> 00:33:01.919
So this is an opinionated feature, which assumes that
00:33:01.920 --> 00:33:05.399
you're likely going to want to review the output
00:33:05.400 --> 00:33:10.559
immediately, or that you often will. Of course, you can
00:33:10.560 --> 00:33:17.599
always jump to the end.
00:33:19.980 --> 00:33:23.919
Also, after a command is entered, the cursor is immediately
00:33:23.920 --> 00:33:28.279
repositioned to make it easy to edit the command.
00:33:53.020 --> 00:33:56.519
And also, if I don't want to edit the command, and I do not want
00:33:56.520 --> 00:33:59.679
to review the output, I can simply start typing another
00:33:59.680 --> 00:34:00.359
command.
00:34:11.260 --> 00:34:15.519
So that covers the brief tour of Eshell features.
00:34:17.760 --> 00:34:21.127
And that basically ends my talk.
NOTE Login shell
00:34:21.128 --> 00:34:22.380
However, a handful of
00:34:22.381 --> 00:34:28.719
viewers might be wondering, is it possible to set Emacs to be
00:34:28.720 --> 00:34:37.639
my login shell to completely replace bash in your login
00:34:37.640 --> 00:34:43.719
experience? The answer is yes, but in practice there are
00:34:43.720 --> 00:34:47.399
various difficulties involved which might make it not
00:34:47.400 --> 00:34:48.359
worth the trouble.
00:35:00.440 --> 00:35:03.479
Before doing this, you'll have to answer a few initial
00:35:03.480 --> 00:35:09.519
questions. Do you want to make a new Emacs instance every
00:35:09.520 --> 00:35:13.759
time you log in, or do you want it to connect to an Emacs
00:35:13.760 --> 00:35:20.599
server? Which is popular among Emacs users, to reuse the
00:35:20.600 --> 00:35:26.599
session, or to connect to the existing session. Also, do you
00:35:26.600 --> 00:35:30.639
want a different result, whether in graphical or a terminal
00:35:30.640 --> 00:35:34.679
environment? And are you okay with your initialization
00:35:34.680 --> 00:35:39.559
file being run every time you log in, including every new tab
00:35:39.560 --> 00:35:44.520
you open in a terminal emulator? If we assume that you are
00:35:44.521 --> 00:35:50.339
using a system with /etc/passwd user management, you get
00:35:50.340 --> 00:35:53.999
one field to specify the name of the shell program that you
00:35:54.000 --> 00:35:58.479
want to use, and no arguments are allowed. So maybe you can
00:35:58.480 --> 00:36:02.679
see how this might be challenging, depending on your
00:36:02.680 --> 00:36:06.879
answers to the previous questions. You can work around
00:36:06.880 --> 00:36:10.479
these issues in various ways, like modifying the
00:36:10.480 --> 00:36:15.439
authentication system, or by specifying a script for your
00:36:15.440 --> 00:36:21.799
login shell. But if your normal workflow is to simply log in
00:36:21.800 --> 00:36:25.679
and start Emacs and run that Emacs session until your next
00:36:25.680 --> 00:36:36.979
reboot, then it probably isn't worth the bother.
NOTE Resources
00:36:36.980 --> 00:36:41.999
So thank you for listening to my talk, Emacs as a Shell, by
00:36:42.000 --> 00:36:46.319
Christopher Howard for Emacs Conference 2024.
00:36:46.860 --> 00:36:51.519
At the bottom of this page, you can see a link to the
00:36:51.520 --> 00:36:56.919
repository containing the brief amount of code that was
00:36:56.920 --> 00:37:03.679
featured here in this video, as well as a link to my personal
00:37:03.680 --> 00:37:10.279
Gemini gemlog, as well as to a Web portal version of that.
00:37:10.280 --> 00:37:13.000
Thank you.
