WEBVTT 00:00.720 --> 00:06.540 Now that we can see and monitor processes, let's gain some control over them. 00:06.540 --> 00:13.300 So for our experiments, we are going to use a little program called X Logo as our guinea pig. 00:13.320 --> 00:20.430 So the X logo program is a simple and sample program supplied with the X window system and the underlying 00:20.430 --> 00:26.220 engine that makes the graphics on our display go, which simply displays a resizable window containing 00:26.220 --> 00:26.910 the x logo. 00:26.910 --> 00:33.780 Here you will enter x logo here and as you can see here, that's our X program right here. 00:33.780 --> 00:35.120 You can resize this. 00:35.130 --> 00:36.270 Oops, where'd it go? 00:36.270 --> 00:36.630 Here. 00:36.630 --> 00:40.740 So you can resize this, right that and drag this down. 00:40.740 --> 00:42.900 So actually it doesn't have any functions. 00:43.020 --> 00:45.540 It's just a sample and dummy program. 00:45.540 --> 00:50.550 So after entering the command, the small window containing the logo should appear somewhere on the 00:50.550 --> 00:57.390 screen here on some systems X logo might print a warning message, but it can safely be ignored. 00:57.390 --> 01:02.500 And if your system does not include X logo program, try gedit. 01:03.370 --> 01:04.510 Actually, let's close this. 01:04.510 --> 01:14.020 So try gedit or as you can see it asks me to install or you can also use the gedit. 01:14.020 --> 01:16.900 And here the second program was. 01:21.090 --> 01:21.420 Actual. 01:21.420 --> 01:22.650 The second program was key. 01:22.680 --> 01:22.890 Right. 01:22.890 --> 01:23.540 Yeah, right. 01:23.550 --> 01:23.970 Your key. 01:23.970 --> 01:24.540 Right. 01:25.390 --> 01:27.970 Here as we let's install the key right now. 01:27.970 --> 01:29.530 Enter our password. 01:29.560 --> 01:31.900 Yes, it's 175MB. 01:31.900 --> 01:36.760 I think the that is going to be much less in size. 01:37.570 --> 01:39.370 Edit Yes. 01:40.060 --> 01:41.980 As you can see, it's 50MB. 01:41.980 --> 01:47.860 And you can also open just another window in from your tab here. 01:47.860 --> 01:53.050 In this case, let's actually we can also use the screen recording for just for just example here. 01:53.050 --> 01:56.740 But in most systems, the X logo is comes with default. 01:56.740 --> 01:58.090 So you don't have to install it. 01:58.330 --> 02:01.930 Probably it has in your system Linux system here. 02:01.930 --> 02:09.070 So we can verify that the x log is running by resizing and its window if the log is redrawn in the new 02:09.070 --> 02:16.900 size like this and here like this, then it means the program is running. 02:16.900 --> 02:22.600 So notice how our shell prompt has not returned, as you can see here, just doing a sync. 02:22.600 --> 02:28.870 So this is because the shell is waiting for the program to finish, just like all other programs we 02:28.870 --> 02:30.070 have used so far. 02:30.070 --> 02:33.820 So if we close the X logo window right here. 02:35.060 --> 02:40.940 As you can see here, the prompt returns and we can enter a new command in this prompt here. 02:40.940 --> 02:44.480 So let's observe what happens when we run X log again. 02:44.480 --> 02:50.840 So first, enter the X log command and verify that the program is running. 02:50.840 --> 02:54.140 Next, return the terminal window and control. 02:54.350 --> 02:59.390 Actually, let's actually see happens right here and make it X logo. 03:00.280 --> 03:02.440 Here and now. 03:02.440 --> 03:03.820 We're going to in-terminal. 03:03.830 --> 03:06.250 We're going to press control. 03:07.810 --> 03:10.270 Quantum control. 03:13.020 --> 03:13.360 Thompson. 03:17.420 --> 03:18.880 And see. 03:18.920 --> 03:20.150 Command and see. 03:20.150 --> 03:20.360 Let's. 03:20.630 --> 03:22.550 Let's see what happens right here. 03:23.950 --> 03:26.050 And that's it here, as you can see in terminal. 03:26.410 --> 03:28.270 We press the Ctrl key. 03:28.750 --> 03:33.010 When you press any programming control C, it will interrupt a program. 03:33.010 --> 03:39.580 So this means we are politely asking the program to terminate after we press Ctrl C, the x log of windows 03:39.610 --> 03:43.690 is closed here and the shell prompt returned. 03:43.840 --> 03:50.560 Many, but not all common line programs can be interrupted by using this technique. 03:50.590 --> 03:53.770 Let's actually put a process in the background right now. 03:53.770 --> 03:59.260 So let's say we wanted to get the shell prompt back without terminating the program. 03:59.260 --> 04:00.610 We can do this. 04:00.790 --> 04:02.800 Actually, we can do this. 04:04.540 --> 04:06.790 By placing the program in the background. 04:07.920 --> 04:14.480 A think of the thermal as having a foreground with the stuff visible on the surface, like the shell 04:14.480 --> 04:22.490 prompt and the background with the stuff hidden behind the surface to launch a program so that it it 04:22.490 --> 04:25.940 is immediately, immediately placed in the background. 04:25.970 --> 04:35.390 We will use this command X logo and operator X logo and operator ampersand character here enter. 04:35.390 --> 04:42.860 And as you can see here, we now enter the shell and we also opened our X logo without terminating it. 04:42.860 --> 04:47.630 So after entering the command X logo, window appeared, as you can see here, and the shell prompt 04:47.630 --> 04:48.980 is returned. 04:48.980 --> 04:51.800 But some funny numbers were printed right here. 04:51.980 --> 04:59.480 So this matches is a part of a shell feature feature called the Job Control. 05:00.340 --> 05:00.740 Your. 05:01.800 --> 05:02.580 Job. 05:04.030 --> 05:04.930 Control. 05:09.230 --> 05:09.710 So. 05:10.640 --> 05:12.410 The job control with this message. 05:12.410 --> 05:18.680 The Shell is telling us that we have a started job number. 05:19.640 --> 05:26.810 Job number one and that it has process ID So this is a job number and this is a process ID after job 05:26.810 --> 05:31.780 number is 12,496. 05:31.790 --> 05:35.330 So if we run the PS command right here. 05:35.330 --> 05:35.620 Yeah. 05:35.630 --> 05:40.070 If we run the PS command right now, we can see our processes. 05:40.580 --> 05:41.360 That's it. 05:42.240 --> 05:47.520 12 496 12 496 and X logo. 05:47.520 --> 05:47.760 Here. 05:47.760 --> 05:50.280 As you can see, our program name is writing right here. 05:50.310 --> 05:56.460 So the Shell job control facility also gives us a way to list the jobs that have been launched from 05:56.460 --> 05:57.380 our terminal. 05:57.390 --> 06:04.380 So using the jobs command, using the jobs command, we can see this list right here. 06:04.380 --> 06:14.190 So the result shows that we have one job number one that it is running and that the command was X logon. 06:16.560 --> 06:19.100 Let's now return the process to the foreground. 06:19.110 --> 06:22.710 So a process in the background is. 06:22.710 --> 06:29.740 You mean you mean from terminal keyboard input, including any attempt to interrupt it with the control 06:29.790 --> 06:30.420 C here. 06:30.420 --> 06:33.810 As you can see, whenever we click Ctrl C it does not. 06:34.140 --> 06:35.910 It happens nothing here actually. 06:35.910 --> 06:43.680 Let's make it always on top and make it right here so it will not disappear right as it did in previous 06:43.680 --> 06:44.130 here. 06:44.640 --> 06:46.650 Clear the clear. 06:51.030 --> 06:55.050 As I said, it processes in the background is immune from terminal keyboard input. 06:55.050 --> 06:57.720 So to return a process to the foreground. 06:58.570 --> 07:00.250 Use the f g. 07:01.290 --> 07:02.880 Command in this way. 07:02.910 --> 07:07.410 So first, you're going to enter the jobs here to see what is is here. 07:07.410 --> 07:13.110 And now we're going to use the FG and percentage and one. 07:13.890 --> 07:22.080 Here, As you can see here, the FG command followed by a present sign on the job number called a job 07:22.080 --> 07:23.870 spec does a trick. 07:23.880 --> 07:29.670 So if we only have one background job, the job spec is optional too. 07:29.670 --> 07:32.700 To terminate the x logo here. 07:33.790 --> 07:42.370 Uh, you will press the control C here and it will terminate our process that we used in background. 07:42.760 --> 07:45.910 We can also pause or stop a process. 07:45.910 --> 07:52.060 So sometimes we will want to stop a process without terminating it, which you will learn in next lecture. 07:52.060 --> 07:53.710 How to stop a process. 07:53.710 --> 07:55.360 So I'm waiting you in next lecture.