WEBVTT 00:00.970 --> 00:03.490 So you can run commands at a prompt. 00:03.490 --> 00:05.290 But what is that prompt? 00:05.320 --> 00:06.610 Where does that come from? 00:06.610 --> 00:10.580 How are your commands going to run and why does it matter? 00:10.600 --> 00:14.160 You will get an answer for these questions in this lecture. 00:14.170 --> 00:15.240 My name is Stephan. 00:15.250 --> 00:17.110 Welcome to another lecture of our course. 00:17.110 --> 00:18.250 Let's get started. 00:30.720 --> 00:35.620 That little prompt is produced by a program called Shell. 00:35.640 --> 00:40.990 Let's actually get our diagram here so we can write things better on screen. 00:41.070 --> 00:48.450 So here so the so the little prompt is produced by a program called Shell. 00:53.650 --> 00:54.280 Shell. 00:54.520 --> 01:01.470 So it's a user interface that sits between you and the Linux interface here. 01:01.480 --> 01:08.080 So here, for example, in the left side is this is you here and here. 01:08.080 --> 01:10.840 This is our famous penguin. 01:10.840 --> 01:13.630 So I can draw Penguin right now, but I will try. 01:13.660 --> 01:14.710 Try here. 01:14.710 --> 01:18.100 So this is our penguin here. 01:20.720 --> 01:22.670 And here, This is our penguin. 01:22.670 --> 01:23.270 Yeah. 01:23.960 --> 01:24.530 Here. 01:24.530 --> 01:30.350 So this is the shell that sits between you and the Linux operating system. 01:30.350 --> 01:32.510 So Linux supplies several shells. 01:32.510 --> 01:38.930 And the most common and the standard for this course is called the bash shell. 01:38.930 --> 01:41.210 So actually, let's actually write this. 01:41.210 --> 01:47.840 So we're going to use that as Oops, yeah, now we're going to use that as a bash shell. 01:47.870 --> 01:54.860 BASH So this is just a standard that while most widely use shell type in Linux here, so Bash and other 01:54.860 --> 02:00.830 shells do much more than simply run commands, for example, for example, actually, let's delete this. 02:00.830 --> 02:01.370 Yeah. 02:01.400 --> 02:03.410 For example. 02:05.440 --> 02:07.750 When a command includes a wild card here. 02:07.750 --> 02:08.920 So this is a wild card. 02:09.640 --> 02:10.610 This is a wild card. 02:10.940 --> 02:11.560 Operator. 02:13.620 --> 02:16.110 Uh, this referred to multiple files at once. 02:16.110 --> 02:21.990 So for example, LHS here, LHS here in let's actually go to bin. 02:21.990 --> 02:24.720 So we have more files on bin here. 02:24.720 --> 02:27.210 So for example, LHS. 02:28.530 --> 02:30.300 Let's find the sea here. 02:30.300 --> 02:33.310 And as you can see, we get sea files. 02:33.390 --> 02:35.340 Not like this, LZ. 02:36.110 --> 02:36.590 Like this. 02:36.590 --> 02:40.280 And as you can see, no such file or directory. 02:40.830 --> 02:47.510 So, for example, the we access the multiple files at once, but in this case we don't have a C file 02:47.510 --> 02:47.840 here. 02:47.840 --> 02:52.970 So let's actually, instead of writing, uh, finding folders, let's go to Python here. 02:52.970 --> 02:57.320 So I think we're going to have Python three point. 02:58.310 --> 02:58.550 Trip. 02:58.580 --> 02:59.930 Python three point. 03:03.680 --> 03:04.580 Yeah, that's. 03:04.580 --> 03:06.770 That's actually fine. 03:06.770 --> 03:08.020 This here. 03:08.030 --> 03:08.870 Let's actually. 03:08.870 --> 03:10.040 Here, here, here. 03:10.250 --> 03:11.260 Open SSL. 03:11.270 --> 03:13.340 So let's go to open SSL. 03:13.370 --> 03:14.810 Open SSL, TLS. 03:14.810 --> 03:17.120 So let's look what we here. 03:17.150 --> 03:21.050 See the open SSL directory? 03:21.080 --> 03:21.470 Yeah. 03:21.510 --> 03:21.710 Open. 03:22.610 --> 03:23.900 Apparently the file. 03:24.230 --> 03:25.790 Yeah, that's it. 03:25.790 --> 03:30.860 So for example, ls something like that you're going to see all of this here. 03:30.860 --> 03:35.690 So the file wild card here, we will use the wild card in the next lectures too. 03:35.690 --> 03:40.850 So the wild card is a handled entirely by the shell, not by the program ls here. 03:40.850 --> 03:43.790 So the shell value is the expression here. 03:43.790 --> 03:51.200 For example, let's actually write this like a clear CD home and Carly. 03:51.230 --> 03:51.590 Oops. 03:52.010 --> 03:52.970 Carly here. 03:52.970 --> 03:53.720 So. 03:54.960 --> 03:56.990 If here, for example, LHS. 04:00.250 --> 04:02.140 Yeah, the R code here. 04:02.140 --> 04:05.380 The wildcard operator, for example, ls the. 04:07.440 --> 04:11.550 Dot py or LZ txt. 04:11.580 --> 04:12.570 We have txt files. 04:12.570 --> 04:12.840 Right? 04:12.840 --> 04:14.370 And as you can see we got on here. 04:14.370 --> 04:23.490 So if we copy this txt files right now and here let's open our text here right now. 04:23.700 --> 04:25.470 Axel txt copy copy here. 04:25.470 --> 04:26.130 Like this. 04:26.130 --> 04:27.720 So now. 04:27.720 --> 04:28.290 Yeah. 04:28.590 --> 04:29.100 Here. 04:29.100 --> 04:31.770 And as you can see, we got all the copies here. 04:31.770 --> 04:34.140 So here. 04:35.320 --> 04:36.520 The wild card. 04:37.280 --> 04:44.360 And as you can see here, the shell evaluates the expression the wild card operator, dot txt and invisible. 04:45.050 --> 04:50.680 Invisible replaces it with a list of matching file names before LHS runs. 04:50.690 --> 04:56.200 So in other words, LHS never sees the wild card here. 04:56.210 --> 05:03.410 So for the perspective of LHS, the type following command is going to be, for example, LHS, the 05:03.440 --> 05:04.040 Oxley. 05:05.210 --> 05:05.480 Oops. 05:05.480 --> 05:12.830 Actually, let's first say yeah, Oxley here, LHS Oxley copy, for example. 05:12.830 --> 05:16.730 Copy one and copy one. 05:16.760 --> 05:17.690 Yes. 05:20.390 --> 05:22.970 Or no, we don't have a copy ten for example. 05:22.970 --> 05:29.840 And after that TXT and then it comes Oxitec's or like Oxley again. 05:29.870 --> 05:30.380 Oxley. 05:31.230 --> 05:31.820 Copy. 05:31.850 --> 05:32.680 Oxley. 05:32.720 --> 05:33.590 Copy. 05:33.650 --> 05:34.370 TXT. 05:36.230 --> 05:37.520 Copy, for example. 05:37.520 --> 05:38.210 Yeah. 05:38.390 --> 05:40.490 8 or 6 here. 05:40.610 --> 05:42.290 Okay, so copy like this. 05:42.290 --> 05:44.300 And here, as you can see, we got an error. 05:44.300 --> 05:48.770 So our this wildcard operator sees like this. 05:48.770 --> 05:55.880 So the shell also handles pipes, as you saw in the first section of our this course. 05:55.880 --> 06:03.920 So it redirects the STD in an STD and transparently so the that the programs involves have no idea they 06:03.920 --> 06:05.780 are communicating with each other. 06:05.780 --> 06:13.660 So every time a command runs, some steps are the responsibility of the invoked programs such as LHS. 06:13.670 --> 06:17.360 So at some there are the responsibility. 06:18.770 --> 06:24.440 Uh, here are the responsible of the shell, so expert users understand which is which. 06:24.440 --> 06:31.430 So that's one reason they create a long, complex command of the top of their head and run them successfully. 06:31.430 --> 06:36.000 So they already know what the command will do before they pass. 06:36.000 --> 06:36.900 Uh, press enter. 06:36.900 --> 06:43.770 So in part because they understand that separation between shell and programs it invokes. 06:43.770 --> 06:47.340 So in this lecture we will launch you understanding of the Linux shell. 06:47.340 --> 06:53.160 I will take the same minimalistic approach I use for commands and pipes in previous lectures rather 06:53.160 --> 06:55.140 than cover dozens of shell features. 06:55.140 --> 07:02.610 And I will hand you just enough information to carry you to the next step of our learning journey. 07:02.610 --> 07:08.460 So in this lecture you will learn about the pattern matching for file names, you will learn redirection 07:08.460 --> 07:09.930 of input and outputs. 07:09.930 --> 07:15.990 You will learn variables to store valuables quoting and escaping to disable certain shell features. 07:15.990 --> 07:19.920 The search path for locating programs to run and you. 07:19.920 --> 07:24.240 Lastly, you will learn how to save changes to your shell environment. 07:24.240 --> 07:26.220 So I'm waiting you in the next lecture. 07:26.220 --> 07:27.120 See you later.