diff options
Diffstat (limited to '')
| -rw-r--r-- | 2024/captions/emacsconf-2024-shell--emacs-as-a-shell--christopher-howard--main.vtt | 1142 |
1 files changed, 1142 insertions, 0 deletions
diff --git a/2024/captions/emacsconf-2024-shell--emacs-as-a-shell--christopher-howard--main.vtt b/2024/captions/emacsconf-2024-shell--emacs-as-a-shell--christopher-howard--main.vtt new file mode 100644 index 00000000..7f16a859 --- /dev/null +++ b/2024/captions/emacsconf-2024-shell--emacs-as-a-shell--christopher-howard--main.vtt @@ -0,0 +1,1142 @@ +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. |