1 00:00:00,500 --> 00:00:02,630 Reading, writing and executing. 2 00:00:02,630 --> 00:00:11,240 So access rights to files and directories are defined in terms of read access, write access and execution 3 00:00:11,240 --> 00:00:11,870 access. 4 00:00:11,870 --> 00:00:19,670 So if we look at the output of the command right here and you will see here LSL here, so you will see 5 00:00:19,670 --> 00:00:25,640 here that we can see, we can get some clue as how this is implemented. 6 00:00:25,640 --> 00:00:32,540 So in previous lectures we learned about file attributes and the first characters is the file type. 7 00:00:33,550 --> 00:00:37,690 So the file type describes the file types you are most likely to see. 8 00:00:37,690 --> 00:00:41,170 And there are other less common types to do. 9 00:00:41,170 --> 00:00:43,360 For example, this here. 10 00:00:43,390 --> 00:00:45,100 This means a regular file. 11 00:00:45,280 --> 00:00:47,650 This first attributes means here. 12 00:00:47,650 --> 00:00:54,130 So let me actually write that down here and you will see what is going on here. 13 00:00:54,130 --> 00:00:59,540 So the minus here means a regular file. 14 00:00:59,570 --> 00:01:01,900 Regular file. 15 00:01:01,900 --> 00:01:03,820 And as you can see here, some of examples. 16 00:01:03,820 --> 00:01:09,340 For example, my file, my name here, this might be like my new dear back, but the name. 17 00:01:09,340 --> 00:01:10,230 Just a minute. 18 00:01:10,390 --> 00:01:11,410 It's actually a file. 19 00:01:11,410 --> 00:01:15,490 And as you can see here, it starts with this attribute. 20 00:01:15,880 --> 00:01:21,580 All of the files starts with the, uh, the regular file starts with this attributes. 21 00:01:21,610 --> 00:01:26,230 We also have notice here we have a directory. 22 00:01:27,260 --> 00:01:28,670 Directory here. 23 00:01:30,210 --> 00:01:33,060 The IS directory. 24 00:01:35,670 --> 00:01:37,280 And we also have l. 25 00:01:37,380 --> 00:01:38,810 This is a symbol. 26 00:01:38,820 --> 00:01:41,850 This is for the symbolic links that we learned earlier. 27 00:01:41,850 --> 00:01:48,960 In this case, we don't have symbolic links and we will create that symbolic symbolic link. 28 00:01:50,040 --> 00:01:54,000 See here means a character special file. 29 00:01:55,050 --> 00:01:55,620 Here. 30 00:01:55,650 --> 00:02:00,510 This is a character special file. 31 00:02:00,510 --> 00:02:08,880 And this file type refers to a device that handles data as a stream of bytes such as terminal or dev 32 00:02:08,880 --> 00:02:09,540 null. 33 00:02:09,540 --> 00:02:17,340 And we also have B, the B is for a special file block, special file block, special file. 34 00:02:17,340 --> 00:02:24,180 And this file types refer to a device that handles data in blocks such as hard drives or DVD drives. 35 00:02:24,180 --> 00:02:30,330 So the remaining nine characters of the file attributes called the file mode here, actually let me 36 00:02:30,330 --> 00:02:31,890 write that down here. 37 00:02:31,890 --> 00:02:35,760 So, for example, let's take this right? 38 00:02:36,740 --> 00:02:37,670 Copy this. 39 00:02:38,690 --> 00:02:39,530 And here. 40 00:02:39,570 --> 00:02:39,960 Oops. 41 00:02:40,940 --> 00:02:41,480 Here. 42 00:02:41,480 --> 00:02:42,820 Open our notepad. 43 00:02:42,830 --> 00:02:43,910 And here. 44 00:02:44,090 --> 00:02:45,260 So this. 45 00:02:45,530 --> 00:02:47,750 This was our directory. 46 00:02:48,050 --> 00:02:50,150 This is a file type directory. 47 00:02:50,150 --> 00:02:50,720 And. 48 00:02:51,110 --> 00:02:54,570 And others are file mode. 49 00:02:54,590 --> 00:03:01,130 So these file modes represents the read, write and execute permissions here. 50 00:03:01,130 --> 00:03:03,750 And actually, let me get my mark here. 51 00:03:03,760 --> 00:03:04,220 Here. 52 00:03:04,220 --> 00:03:06,080 So I can show you better. 53 00:03:07,630 --> 00:03:08,160 Also. 54 00:03:11,050 --> 00:03:14,440 Okay, so let me here. 55 00:03:14,440 --> 00:03:16,810 So this D here. 56 00:03:21,180 --> 00:03:25,590 So these are the file mode here. 57 00:03:25,590 --> 00:03:28,230 So actually, let me write that down here. 58 00:03:28,230 --> 00:03:31,290 So these are file. 59 00:03:32,090 --> 00:03:32,900 Maud. 60 00:03:34,720 --> 00:03:37,120 And the first letter. 61 00:03:37,150 --> 00:03:41,710 The first letter represents us that the represents us. 62 00:03:41,710 --> 00:03:43,180 The file type. 63 00:03:43,750 --> 00:03:44,220 Yeah. 64 00:03:44,230 --> 00:03:45,220 File. 65 00:03:47,250 --> 00:03:47,880 Type. 66 00:03:48,240 --> 00:03:54,660 As I explained, whether it is a regular file directory, symbolic link or cache spatial file or block 67 00:03:54,660 --> 00:03:55,710 spatial file here. 68 00:03:56,890 --> 00:03:57,550 Here. 69 00:03:58,740 --> 00:03:59,430 So. 70 00:04:00,470 --> 00:04:07,960 Uh, and in order to understand that here, first lecture, let me take this down right here. 71 00:04:07,970 --> 00:04:12,500 So the remaining nine characters of file attributes, as I said, is the file mode. 72 00:04:12,590 --> 00:04:16,460 So for the file's owner, the file's group owner or everybody else. 73 00:04:16,460 --> 00:04:24,020 So in this case, for example, it's going to be like, this is for oops, actually, let's here so 74 00:04:24,500 --> 00:04:25,430 one. 75 00:04:30,180 --> 00:04:33,090 That's actually it will be more easier to understand right here. 76 00:04:33,090 --> 00:04:33,810 So. 77 00:04:34,570 --> 00:04:39,610 As I said, this is file type and all of these are. 78 00:04:42,010 --> 00:04:43,450 File permission attributes. 79 00:04:43,450 --> 00:04:50,170 But here the first three, the first three means owner permissions. 80 00:04:50,380 --> 00:04:52,030 The next three. 81 00:04:53,170 --> 00:04:58,720 Means the group permissions, which you will learn all of this about in this section. 82 00:04:58,720 --> 00:05:05,680 And the last means the world that everybody else so the. 83 00:05:06,890 --> 00:05:07,490 Here. 84 00:05:07,490 --> 00:05:09,550 The R here. 85 00:05:09,590 --> 00:05:11,990 R means read. 86 00:05:12,730 --> 00:05:13,570 Read. 87 00:05:14,880 --> 00:05:17,310 The W. 88 00:05:18,130 --> 00:05:20,140 W means. 89 00:05:21,270 --> 00:05:23,780 Execute ops, not execute. 90 00:05:23,790 --> 00:05:25,650 The W means write. 91 00:05:28,060 --> 00:05:32,350 And here x here means. 92 00:05:35,690 --> 00:05:36,440 Execute. 93 00:05:44,550 --> 00:05:48,000 So now let's explain all of this now. 94 00:05:48,000 --> 00:05:48,810 So. 95 00:05:50,810 --> 00:05:59,630 The R here, the R allows a file to be opened and read. 96 00:06:00,080 --> 00:06:06,770 So if this r, you can see this R in a file, for example, in this case this. 97 00:06:07,130 --> 00:06:08,520 Right r. 98 00:06:08,600 --> 00:06:11,770 This means a lot of file to be opened and read. 99 00:06:11,780 --> 00:06:18,140 But if you see this r in directories, this allows a directory contents to be listed if the execute 100 00:06:18,140 --> 00:06:20,030 attribute is also set. 101 00:06:20,060 --> 00:06:22,360 We also have w. 102 00:06:24,650 --> 00:06:26,090 As you learned here. 103 00:06:26,090 --> 00:06:32,410 So the W allows a file to be written or truncated. 104 00:06:32,420 --> 00:06:36,220 However, this attribute does not allow files to be renamed or deleted. 105 00:06:36,230 --> 00:06:45,260 The ability to delete or rename files is determined by directory attributes, and if you see this w 106 00:06:45,260 --> 00:06:52,190 attribute in a directory, this in that in that directory allows a files within a directory to be created, 107 00:06:52,190 --> 00:06:54,440 deleted and renamed here. 108 00:06:54,440 --> 00:07:04,010 So here first one we learned about the file with this w and now so if you open this, if you use this 109 00:07:04,040 --> 00:07:13,280 in directories, you will get gain an access to create, delete and renamed and if the execute arbitrary 110 00:07:13,280 --> 00:07:17,570 is set or actually dir. 111 00:07:18,800 --> 00:07:24,870 So we also have we also have let me here. 112 00:07:28,020 --> 00:07:28,290 Oops. 113 00:07:28,290 --> 00:07:28,950 Yeah, right. 114 00:07:28,980 --> 00:07:29,820 That's actually. 115 00:07:32,460 --> 00:07:34,200 We also have. 116 00:07:34,680 --> 00:07:35,790 The X here. 117 00:07:35,790 --> 00:07:37,150 Actually, let's delete all of this. 118 00:07:37,170 --> 00:07:38,580 So the x? 119 00:07:38,580 --> 00:07:39,690 Just an x. 120 00:07:40,110 --> 00:07:44,500 So this x loves a file to be to. 121 00:07:44,520 --> 00:07:54,420 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 122 00:07:54,420 --> 00:07:55,950 as a program and execute it. 123 00:07:55,950 --> 00:08:03,300 So program files written in scripting languages must also be set as a readable to be executed. 124 00:08:03,300 --> 00:08:09,150 And here if you use this x in directories, this will use a low. 125 00:08:09,180 --> 00:08:11,700 This is the low directory to be entered. 126 00:08:11,700 --> 00:08:15,690 For example, see the my. 127 00:08:17,290 --> 00:08:17,740 There. 128 00:08:18,880 --> 00:08:27,220 So if you use this in directory X in directory, you can enter and in that directory here.