WEBVTT 00:01.080 --> 00:08.580 Modern operating systems are usually multitasking, meaning that they create the illusion of doing more 00:08.580 --> 00:15.090 than one thing at once by rapidly switching from one execution to another. 00:15.850 --> 00:20.170 So the kernel manages this truth, the use of the processes. 00:20.170 --> 00:27.140 So the processes are how Linux organizes the different programs waiting for their turn at the CPU. 00:27.160 --> 00:31.990 So sometimes a computer will become sluggish on our application will stop responding. 00:31.990 --> 00:37.630 In this section you will learn and we will look at some of the tools available at the command line that 00:37.630 --> 00:45.610 lets us examine what programs are doing and how to terminate processes that are misbehaving. 00:45.610 --> 00:54.280 In this section, you will learn about command, top command, and you will also learn about the jobs. 00:55.360 --> 01:01.310 BG which, uh, the jobs here will list active jobs. 01:01.330 --> 01:05.390 BG Place a job in the background. 01:05.520 --> 01:06.280 EFG. 01:07.740 --> 01:08.940 A place, a job. 01:09.900 --> 01:12.300 In the foreground and kill. 01:12.300 --> 01:18.420 With this kill command, you will send a signal to a process and kill all here. 01:18.450 --> 01:21.980 Kill all the you will send. 01:21.990 --> 01:25.580 Kill the process by name and shut down. 01:25.590 --> 01:26.820 Shut down. 01:27.710 --> 01:32.150 Here you will shut down your computer. 01:32.160 --> 01:34.860 Actually, I don't want to shut down right now. 01:34.860 --> 01:37.410 So let's see what happens when I talk. 01:37.410 --> 01:41.760 So actually, let's learn about how a process works. 01:41.760 --> 01:49.230 So when a system starts up, the kernel initiates a few of its own activities as processes and launches 01:49.230 --> 01:59.520 a program called Init in turn runs a series of shell scripts located in here and are called the init 01:59.520 --> 01:59.820 scripts. 01:59.820 --> 02:06.060 Actually, let's terminate the shutdown process right now with C and as you can see, we terminate the 02:06.060 --> 02:16.330 shutdown process, clear the console and let's CD to ATC here, LZ and these are our shell scripts and 02:16.330 --> 02:20.590 some of these scripts called Init Scripts, which starts all the system services. 02:20.590 --> 02:26.920 So many of these services are implemented as a daemon programs, the programs that just sit in the background 02:26.920 --> 02:30.310 and do their thing without having any user interface. 02:30.310 --> 02:39.070 So even if we are not logged in, the system is at least a little busy performing routine stuff. 02:39.070 --> 02:46.630 So the fact that a program can launch other programs is expressed in the process stream as a parent 02:46.630 --> 02:49.540 process producing a child process. 02:49.540 --> 02:56.650 So the kernel maintains information about each process to help to keep things organized. 02:56.650 --> 03:03.760 So, for example, each process is assigned a number called process ID and process IDs are assigned 03:03.760 --> 03:05.080 in ascending order. 03:05.080 --> 03:12.640 So with init always getting process ID one, so the kernel also keeps track of the memory assigned to 03:12.640 --> 03:20.410 each process and these these each process readiness and resume execution here. 03:21.310 --> 03:29.590 So like files persons also have owners and user IDs if and also effective user IDs and so on. 03:29.590 --> 03:35.230 So let's actually start with viewing our processes right now here. 03:36.170 --> 03:36.920 Clear. 03:36.920 --> 03:40.310 And here you can view the process with PS command. 03:40.310 --> 03:42.860 And as you can see, we get just two processes, right? 03:43.400 --> 03:50.240 So the most commonly used command to view process and there are actually several commands and the most 03:50.240 --> 03:57.200 common use is PS, So the PS program has a lot of options, but in its simplest form it is used like 03:57.200 --> 03:57.680 this. 03:57.980 --> 04:09.020 So the result in this example lists two processes the process 13709 and process 23501. 04:09.980 --> 04:16.430 As we can see by default s doesn't show us very much, right? 04:16.430 --> 04:19.880 So just the process associated with the current terminal session. 04:21.140 --> 04:23.900 And to see more, we need to add some options. 04:23.900 --> 04:27.950 However, before we do that, let's look at the other fields produced by P. 04:27.950 --> 04:28.310 S. 04:28.310 --> 04:32.060 So theta is short for actually let me write that down here. 04:32.060 --> 04:33.320 So t. 04:34.110 --> 04:36.120 He I. 04:37.340 --> 04:42.890 Is short for teletype and refers to controlling terminal for the process. 04:42.890 --> 04:51.470 So Unix is showing its age here, so the time field is the amount of the time field is the amount. 04:52.360 --> 04:55.450 A of CPU time consumed by the process. 04:55.450 --> 04:59.950 So as we can see, neither process makes the computer work very hard. 04:59.950 --> 05:00.370 Right. 05:00.370 --> 05:02.140 Actually and as you can see here. 05:02.140 --> 05:09.070 So if we add an option like this, p x, and as you can see here, we get an A bigger picture of what 05:09.070 --> 05:10.180 the system is doing. 05:10.870 --> 05:13.260 So adding the option. 05:13.270 --> 05:18.730 Note that there is no leading dash in this exception with just an X here. 05:19.770 --> 05:21.650 So let's run it again. 05:21.660 --> 05:27.060 Clear and ps6 X here. 05:27.060 --> 05:31.710 So there's the x command we entered is without a dash. 05:33.730 --> 05:34.330 So. 05:36.330 --> 05:42.780 And this tells us to show all of our process regardless of what terminal, if any, they are controlled 05:42.780 --> 05:43.150 by. 05:43.170 --> 05:51.210 So the presence of a question mark here, the presence of the question mark in the team, as I said 05:51.240 --> 05:54.000 to is actually teletype. 05:54.000 --> 06:01.080 So the question mark is a column in this column indicates here, actually, let me take my marker. 06:01.080 --> 06:08.070 So in this command, the question marks in this column indicates. 06:09.180 --> 06:10.500 No controlling terminal. 06:10.620 --> 06:16.780 So using this option, we can list every process that we own. 06:16.800 --> 06:24.960 So because a system is running a lot of processes, PS produced, PS produced a long list, so it is 06:24.960 --> 06:31.980 often helpful to pipe the output from PS into less so for easy viewing. 06:32.010 --> 06:32.430 Of course. 06:32.430 --> 06:38.910 So some options combinations also produce a long lines of output, so maximizing the terminal emulator 06:38.910 --> 06:42.030 window might be a good idea too. 06:42.720 --> 06:48.240 And in next lecture you will learn about more in PS and processes. 06:48.240 --> 06:49.800 So I'm waiting you in next lecture.