WEBVTT 00:00.500 --> 00:02.630 Reading, writing and executing. 00:02.630 --> 00:11.240 So access rights to files and directories are defined in terms of read access, write access and execution 00:11.240 --> 00:11.870 access. 00:11.870 --> 00:19.670 So if we look at the output of the command right here and you will see here LSL here, so you will see 00:19.670 --> 00:25.640 here that we can see, we can get some clue as how this is implemented. 00:25.640 --> 00:32.540 So in previous lectures we learned about file attributes and the first characters is the file type. 00:33.550 --> 00:37.690 So the file type describes the file types you are most likely to see. 00:37.690 --> 00:41.170 And there are other less common types to do. 00:41.170 --> 00:43.360 For example, this here. 00:43.390 --> 00:45.100 This means a regular file. 00:45.280 --> 00:47.650 This first attributes means here. 00:47.650 --> 00:54.130 So let me actually write that down here and you will see what is going on here. 00:54.130 --> 00:59.540 So the minus here means a regular file. 00:59.570 --> 01:01.900 Regular file. 01:01.900 --> 01:03.820 And as you can see here, some of examples. 01:03.820 --> 01:09.340 For example, my file, my name here, this might be like my new dear back, but the name. 01:09.340 --> 01:10.230 Just a minute. 01:10.390 --> 01:11.410 It's actually a file. 01:11.410 --> 01:15.490 And as you can see here, it starts with this attribute. 01:15.880 --> 01:21.580 All of the files starts with the, uh, the regular file starts with this attributes. 01:21.610 --> 01:26.230 We also have notice here we have a directory. 01:27.260 --> 01:28.670 Directory here. 01:30.210 --> 01:33.060 The IS directory. 01:35.670 --> 01:37.280 And we also have l. 01:37.380 --> 01:38.810 This is a symbol. 01:38.820 --> 01:41.850 This is for the symbolic links that we learned earlier. 01:41.850 --> 01:48.960 In this case, we don't have symbolic links and we will create that symbolic symbolic link. 01:50.040 --> 01:54.000 See here means a character special file. 01:55.050 --> 01:55.620 Here. 01:55.650 --> 02:00.510 This is a character special file. 02:00.510 --> 02:08.880 And this file type refers to a device that handles data as a stream of bytes such as terminal or dev 02:08.880 --> 02:09.540 null. 02:09.540 --> 02:17.340 And we also have B, the B is for a special file block, special file block, special file. 02:17.340 --> 02:24.180 And this file types refer to a device that handles data in blocks such as hard drives or DVD drives. 02:24.180 --> 02:30.330 So the remaining nine characters of the file attributes called the file mode here, actually let me 02:30.330 --> 02:31.890 write that down here. 02:31.890 --> 02:35.760 So, for example, let's take this right? 02:36.740 --> 02:37.670 Copy this. 02:38.690 --> 02:39.530 And here. 02:39.570 --> 02:39.960 Oops. 02:40.940 --> 02:41.480 Here. 02:41.480 --> 02:42.820 Open our notepad. 02:42.830 --> 02:43.910 And here. 02:44.090 --> 02:45.260 So this. 02:45.530 --> 02:47.750 This was our directory. 02:48.050 --> 02:50.150 This is a file type directory. 02:50.150 --> 02:50.720 And. 02:51.110 --> 02:54.570 And others are file mode. 02:54.590 --> 03:01.130 So these file modes represents the read, write and execute permissions here. 03:01.130 --> 03:03.750 And actually, let me get my mark here. 03:03.760 --> 03:04.220 Here. 03:04.220 --> 03:06.080 So I can show you better. 03:07.630 --> 03:08.160 Also. 03:11.050 --> 03:14.440 Okay, so let me here. 03:14.440 --> 03:16.810 So this D here. 03:21.180 --> 03:25.590 So these are the file mode here. 03:25.590 --> 03:28.230 So actually, let me write that down here. 03:28.230 --> 03:31.290 So these are file. 03:32.090 --> 03:32.900 Maud. 03:34.720 --> 03:37.120 And the first letter. 03:37.150 --> 03:41.710 The first letter represents us that the represents us. 03:41.710 --> 03:43.180 The file type. 03:43.750 --> 03:44.220 Yeah. 03:44.230 --> 03:45.220 File. 03:47.250 --> 03:47.880 Type. 03:48.240 --> 03:54.660 As I explained, whether it is a regular file directory, symbolic link or cache spatial file or block 03:54.660 --> 03:55.710 spatial file here. 03:56.890 --> 03:57.550 Here. 03:58.740 --> 03:59.430 So. 04:00.470 --> 04:07.960 Uh, and in order to understand that here, first lecture, let me take this down right here. 04:07.970 --> 04:12.500 So the remaining nine characters of file attributes, as I said, is the file mode. 04:12.590 --> 04:16.460 So for the file's owner, the file's group owner or everybody else. 04:16.460 --> 04:24.020 So in this case, for example, it's going to be like, this is for oops, actually, let's here so 04:24.500 --> 04:25.430 one. 04:30.180 --> 04:33.090 That's actually it will be more easier to understand right here. 04:33.090 --> 04:33.810 So. 04:34.570 --> 04:39.610 As I said, this is file type and all of these are. 04:42.010 --> 04:43.450 File permission attributes. 04:43.450 --> 04:50.170 But here the first three, the first three means owner permissions. 04:50.380 --> 04:52.030 The next three. 04:53.170 --> 04:58.720 Means the group permissions, which you will learn all of this about in this section. 04:58.720 --> 05:05.680 And the last means the world that everybody else so the. 05:06.890 --> 05:07.490 Here. 05:07.490 --> 05:09.550 The R here. 05:09.590 --> 05:11.990 R means read. 05:12.730 --> 05:13.570 Read. 05:14.880 --> 05:17.310 The W. 05:18.130 --> 05:20.140 W means. 05:21.270 --> 05:23.780 Execute ops, not execute. 05:23.790 --> 05:25.650 The W means write. 05:28.060 --> 05:32.350 And here x here means. 05:35.690 --> 05:36.440 Execute. 05:44.550 --> 05:48.000 So now let's explain all of this now. 05:48.000 --> 05:48.810 So. 05:50.810 --> 05:59.630 The R here, the R allows a file to be opened and read. 06:00.080 --> 06:06.770 So if this r, you can see this R in a file, for example, in this case this. 06:07.130 --> 06:08.520 Right r. 06:08.600 --> 06:11.770 This means a lot of file to be opened and read. 06:11.780 --> 06:18.140 But if you see this r in directories, this allows a directory contents to be listed if the execute 06:18.140 --> 06:20.030 attribute is also set. 06:20.060 --> 06:22.360 We also have w. 06:24.650 --> 06:26.090 As you learned here. 06:26.090 --> 06:32.410 So the W allows a file to be written or truncated. 06:32.420 --> 06:36.220 However, this attribute does not allow files to be renamed or deleted. 06:36.230 --> 06:45.260 The ability to delete or rename files is determined by directory attributes, and if you see this w 06:45.260 --> 06:52.190 attribute in a directory, this in that in that directory allows a files within a directory to be created, 06:52.190 --> 06:54.440 deleted and renamed here. 06:54.440 --> 07:04.010 So here first one we learned about the file with this w and now so if you open this, if you use this 07:04.040 --> 07:13.280 in directories, you will get gain an access to create, delete and renamed and if the execute arbitrary 07:13.280 --> 07:17.570 is set or actually dir. 07:18.800 --> 07:24.870 So we also have we also have let me here. 07:28.020 --> 07:28.290 Oops. 07:28.290 --> 07:28.950 Yeah, right. 07:28.980 --> 07:29.820 That's actually. 07:32.460 --> 07:34.200 We also have. 07:34.680 --> 07:35.790 The X here. 07:35.790 --> 07:37.150 Actually, let's delete all of this. 07:37.170 --> 07:38.580 So the x? 07:38.580 --> 07:39.690 Just an x. 07:40.110 --> 07:44.500 So this x loves a file to be to. 07:44.520 --> 07:54.420 And by the way, if you use this x in a file, a file loves a file to create a program as a create treat 07:54.420 --> 07:55.950 as a program and execute it. 07:55.950 --> 08:03.300 So program files written in scripting languages must also be set as a readable to be executed. 08:03.300 --> 08:09.150 And here if you use this x in directories, this will use a low. 08:09.180 --> 08:11.700 This is the low directory to be entered. 08:11.700 --> 08:15.690 For example, see the my. 08:17.290 --> 08:17.740 There. 08:18.880 --> 08:27.220 So if you use this in directory X in directory, you can enter and in that directory here.