1 00:00:00,240 --> 00:00:01,073 In this lesson, 2 00:00:01,073 --> 00:00:03,393 we're going to go over entering commands in shell. 3 00:00:04,830 --> 00:00:06,900 Now, a shell surrounds the core portion 4 00:00:06,900 --> 00:00:09,750 of the operating system, which we call the kernel. 5 00:00:09,750 --> 00:00:11,280 It allows the user to pass commands 6 00:00:11,280 --> 00:00:13,050 and information to the kernel, 7 00:00:13,050 --> 00:00:16,770 and the kernel also responds back to the user via the shell. 8 00:00:16,770 --> 00:00:19,650 Now, the shell can be thought of as an interpreter 9 00:00:19,650 --> 00:00:23,010 between the human and kernel languages. 10 00:00:23,010 --> 00:00:25,230 So it pretty much it translates our commands 11 00:00:25,230 --> 00:00:28,530 into something that the computer can recognize and use. 12 00:00:28,530 --> 00:00:30,090 Now, the first command we're going to go over 13 00:00:30,090 --> 00:00:31,860 is the echo command. 14 00:00:31,860 --> 00:00:33,960 The echo command only repeats 15 00:00:33,960 --> 00:00:36,150 exactly what it's been told to repeat. 16 00:00:36,150 --> 00:00:37,530 So for example, 17 00:00:37,530 --> 00:00:39,157 I'm going to do echo. 18 00:00:39,157 --> 00:00:39,990 "Hello, 19 00:00:42,270 --> 00:00:43,103 world!" 20 00:00:46,110 --> 00:00:47,760 Voila. 21 00:00:47,760 --> 00:00:49,950 Typically, you're going to use echo in the script. 22 00:00:49,950 --> 00:00:53,190 So for example, whenever the script is going through 23 00:00:53,190 --> 00:00:54,660 and completing all these processes, 24 00:00:54,660 --> 00:00:56,670 sometimes you want to displace something to the user. 25 00:00:56,670 --> 00:01:00,360 Just say, "Update complete, update successful." 26 00:01:00,360 --> 00:01:03,000 You're going to use echo and put the information in 27 00:01:03,000 --> 00:01:05,099 after the results are complete. 28 00:01:05,099 --> 00:01:07,020 Next, we'll use the present working directory. 29 00:01:07,020 --> 00:01:08,823 That's simply PWD. 30 00:01:09,840 --> 00:01:10,950 It just lets the user know 31 00:01:10,950 --> 00:01:13,110 which directory there is currently working in. 32 00:01:13,110 --> 00:01:14,310 So for example, me, 33 00:01:14,310 --> 00:01:16,290 I'm currently working in my home directory 34 00:01:16,290 --> 00:01:17,553 under my profile. 35 00:01:18,780 --> 00:01:20,850 Next, we're going to go over the list command. 36 00:01:20,850 --> 00:01:23,550 What this simply does is print out a list 37 00:01:23,550 --> 00:01:25,320 of the files and folders 38 00:01:25,320 --> 00:01:27,683 that are currently in your present working directory. 39 00:01:28,920 --> 00:01:31,614 So as you see, right now, we just have 40 00:01:31,614 --> 00:01:33,977 just a skew of folders that are currently 41 00:01:33,977 --> 00:01:37,500 in the working directory now, desktop, documents, downloads, 42 00:01:37,500 --> 00:01:38,850 music, pictures, et cetera. 43 00:01:39,930 --> 00:01:43,637 If we want to see more information, we're going to do ls -al. 44 00:01:46,620 --> 00:01:51,620 Now, the A portion of it stands for the hidden attribute. 45 00:01:51,720 --> 00:01:54,630 So whenever you use the A option, pretty much, 46 00:01:54,630 --> 00:01:57,720 it lets you see any file or folder that's hidden. 47 00:01:57,720 --> 00:01:59,580 Now, most of these folders aren't hidden 48 00:01:59,580 --> 00:02:00,750 because of security features. 49 00:02:00,750 --> 00:02:03,630 It's more just to keep the folders looking clean 50 00:02:03,630 --> 00:02:05,130 and remove the user from things 51 00:02:05,130 --> 00:02:07,320 that they typically won't be using. 52 00:02:07,320 --> 00:02:10,590 Now, the L, which stands for the long, 53 00:02:10,590 --> 00:02:13,790 what that does is gives us more information, as we can see, 54 00:02:13,790 --> 00:02:15,480 and so if we look at this screen right here, 55 00:02:15,480 --> 00:02:18,600 we'll see a lot of information to the left. 56 00:02:18,600 --> 00:02:22,683 For example, if we look at the top line, we'll see drwx. 57 00:02:24,780 --> 00:02:26,973 Now, the D stands for the directory, 58 00:02:28,110 --> 00:02:30,750 R is read privileges, 59 00:02:30,750 --> 00:02:32,190 W is write privileges, 60 00:02:32,190 --> 00:02:34,410 and X is executables. 61 00:02:34,410 --> 00:02:36,690 Now, going from left to right, 62 00:02:36,690 --> 00:02:39,990 we'll see that there's multiple sections in the fields. 63 00:02:39,990 --> 00:02:41,643 So in the first section, again, 64 00:02:41,643 --> 00:02:43,290 it's going to be either directory. 65 00:02:43,290 --> 00:02:46,620 Now, if you see a dash there, that means that it's a file. 66 00:02:46,620 --> 00:02:51,600 The first set of rwx's, that's for the owner of the folder. 67 00:02:51,600 --> 00:02:53,400 The next set will be for the group. 68 00:02:53,400 --> 00:02:55,800 If there's a group associated to the file, 69 00:02:55,800 --> 00:02:58,260 those are the privileges that the group will have, 70 00:02:58,260 --> 00:03:00,510 and then the last will be for any other user, 71 00:03:00,510 --> 00:03:02,100 so anyone that's not part of the group 72 00:03:02,100 --> 00:03:03,870 and that's not the owner. 73 00:03:03,870 --> 00:03:05,340 The next field's going to be the links, 74 00:03:05,340 --> 00:03:08,103 the amount of links associated to the file or folder. 75 00:03:09,180 --> 00:03:11,580 After that's going to be the owner. 76 00:03:11,580 --> 00:03:13,800 After that's going to be the group associated with it 77 00:03:13,800 --> 00:03:15,810 'cause, typically, when you create a user profile, 78 00:03:15,810 --> 00:03:18,760 they just all automatically get created as a group as well. 79 00:03:19,740 --> 00:03:22,650 Then you're going to see the amount of bytes 80 00:03:22,650 --> 00:03:25,560 and then the date it was last modified or created, 81 00:03:25,560 --> 00:03:28,533 and then, of course, the name of the directory or file. 82 00:03:30,000 --> 00:03:31,320 So the next command we go over 83 00:03:31,320 --> 00:03:33,180 is the change directory command. 84 00:03:33,180 --> 00:03:34,380 Let's simply cd. 85 00:03:34,380 --> 00:03:36,600 We'll go to the etc directory, 86 00:03:36,600 --> 00:03:39,390 and we'll confirm that with the present working directory. 87 00:03:39,390 --> 00:03:42,300 Now, you can see that we're in the etc directory. 88 00:03:42,300 --> 00:03:46,113 Another one that's very useful is the var log file. 89 00:03:49,110 --> 00:03:51,150 Now, this is where all of these system logs 90 00:03:51,150 --> 00:03:54,240 are typically stored, and if we want to list them out, 91 00:03:54,240 --> 00:03:55,340 of course, we know ls, 92 00:03:58,168 --> 00:04:00,360 of course, for more information to see the hidden files 93 00:04:00,360 --> 00:04:02,280 and more information about 'em. 94 00:04:02,280 --> 00:04:03,723 We add those modifiers. 95 00:04:05,280 --> 00:04:07,830 The next command we're going to go over is the touch command. 96 00:04:07,830 --> 00:04:09,210 Now, if the file already exists, 97 00:04:09,210 --> 00:04:11,460 it will update the modification on it, 98 00:04:11,460 --> 00:04:12,960 but if not, it will just create it. 99 00:04:12,960 --> 00:04:14,210 So we'll do touch myfile. 100 00:04:16,529 --> 00:04:18,240 Oh, see, now, we're in the wrong directory. 101 00:04:18,240 --> 00:04:19,410 So we don't have permissions for that. 102 00:04:19,410 --> 00:04:22,743 So let's go back to my home directory. 103 00:04:26,102 --> 00:04:27,185 Touch myfile. 104 00:04:31,980 --> 00:04:33,791 And then we're going to ls it out, 105 00:04:33,791 --> 00:04:35,793 and we can see the myfile was added. 106 00:04:38,760 --> 00:04:41,400 Now, the next command I'm going to go over is the cat command. 107 00:04:41,400 --> 00:04:44,340 Now, it stands for concatenation, 108 00:04:44,340 --> 00:04:47,550 and what it does is print a display of the information 109 00:04:47,550 --> 00:04:48,510 that we're trying to see. 110 00:04:48,510 --> 00:04:51,660 So for example, we're going to look at a host name. 111 00:04:51,660 --> 00:04:54,543 So this file etc/hostname, 112 00:04:55,590 --> 00:04:57,480 it prints everything out on screen. 113 00:04:57,480 --> 00:04:59,370 That file is very small, 114 00:04:59,370 --> 00:05:01,680 and so it shows only what's in that text, 115 00:05:01,680 --> 00:05:03,990 and it's only one line so it's not too much. 116 00:05:03,990 --> 00:05:04,980 Now, there's going to be examples 117 00:05:04,980 --> 00:05:07,410 where we're going to have files that are very long. 118 00:05:07,410 --> 00:05:09,270 So we're going to use the less command, 119 00:05:09,270 --> 00:05:14,270 and we're going to try the var log file, dmesg file. 120 00:05:17,430 --> 00:05:21,423 Now, this file, again, is very long. 121 00:05:22,320 --> 00:05:24,360 So when we use the less command, 122 00:05:24,360 --> 00:05:28,140 it allows us to use the space to scroll entire pages 123 00:05:28,140 --> 00:05:29,790 or we can use the up and down arrow 124 00:05:29,790 --> 00:05:31,950 just to go one line at a time 125 00:05:31,950 --> 00:05:34,690 or, again, the space changes everything 126 00:05:38,400 --> 00:05:39,550 or to do one at a time, 127 00:05:41,160 --> 00:05:43,710 and we use Q to get out of that, 128 00:05:43,710 --> 00:05:45,690 and, again, if you want to see it with the cat, 129 00:05:45,690 --> 00:05:47,400 you'll see that 130 00:05:47,400 --> 00:05:49,740 we can't see everything on there. 131 00:05:49,740 --> 00:05:51,940 It'll just go to the very bottom 132 00:05:53,190 --> 00:05:56,190 of the screen and only show one page. 133 00:05:56,190 --> 00:06:01,190 So the less command, again, is used for longer files. 134 00:06:03,210 --> 00:06:05,133 I'm going to use Q to quit. 135 00:06:06,000 --> 00:06:08,910 Next thing I want to do is go over the vim command. 136 00:06:08,910 --> 00:06:11,700 Now, the vim allows us to edit a file. 137 00:06:11,700 --> 00:06:15,093 So I'm going to use the same file that I had earlier, myfile. 138 00:06:17,370 --> 00:06:18,780 Now, in order to insert information, 139 00:06:18,780 --> 00:06:20,283 we're want to press the I key, 140 00:06:21,390 --> 00:06:24,003 and for this example, we're just going to say, 141 00:06:24,990 --> 00:06:28,833 Hello, this is Jamario. 142 00:06:30,360 --> 00:06:33,338 Okay, now, to get out of there, 143 00:06:33,338 --> 00:06:34,988 we're going to press the escape key, 144 00:06:35,940 --> 00:06:38,373 and to save, we're going to hit the colon, 145 00:06:39,210 --> 00:06:42,453 write, that's wQ, quit, 146 00:06:44,670 --> 00:06:45,971 and using the command from earlier, 147 00:06:45,971 --> 00:06:47,321 we're going to use cat myfile, 148 00:06:48,900 --> 00:06:51,127 and now, we can see the file displays, 149 00:06:51,127 --> 00:06:51,960 "Hello, this is Jamario," 150 00:06:51,960 --> 00:06:54,690 and that's what I just wrote into the file. 151 00:06:54,690 --> 00:06:56,370 Now there's other text editors 152 00:06:56,370 --> 00:06:59,280 that we can use another one being nano. 153 00:06:59,280 --> 00:07:00,600 So we're going to do the same thing, 154 00:07:00,600 --> 00:07:03,693 but we're going to create another file called myfile2. 155 00:07:05,850 --> 00:07:08,970 Now, with nano, you just go right into insert. 156 00:07:08,970 --> 00:07:13,297 So do Hello, I am nano 157 00:07:16,257 --> 00:07:17,120 for this... 158 00:07:20,070 --> 00:07:20,903 Simple enough. 159 00:07:20,903 --> 00:07:22,320 Now, to save your information, 160 00:07:22,320 --> 00:07:24,490 you're going to do Control + O 161 00:07:25,770 --> 00:07:30,030 or you'll confirm that with inner file name to write to, 162 00:07:30,030 --> 00:07:33,393 and to get out of here, we're going to do Control + X, 163 00:07:35,640 --> 00:07:39,200 and again, we're going to view the file. 164 00:07:39,200 --> 00:07:42,270 We want to see, "Hello, I'm using nano for this file." 165 00:07:42,270 --> 00:07:44,823 So it's saved and everything was successful. 166 00:07:45,840 --> 00:07:46,690 Clear the screen. 167 00:07:49,380 --> 00:07:52,590 Now, there are going to be times that we need access files 168 00:07:52,590 --> 00:07:55,350 that a regular standard user won't be able to access. 169 00:07:55,350 --> 00:07:58,410 So then we're going to have to switch to the root user 170 00:07:58,410 --> 00:08:00,210 to get that information. 171 00:08:00,210 --> 00:08:02,640 So let's try this out really quick, 172 00:08:02,640 --> 00:08:07,640 cat/var/log/boot.log. 173 00:08:08,550 --> 00:08:11,580 Now, we see that we can't do this as a standard user. 174 00:08:11,580 --> 00:08:13,560 So what we need to do is switch to the root. 175 00:08:13,560 --> 00:08:17,727 So we're going to use the command su - root, 176 00:08:17,727 --> 00:08:20,103 and the su stands for substitute user. 177 00:08:21,720 --> 00:08:24,540 So here, we're going to put in the root password, 178 00:08:24,540 --> 00:08:25,833 and now, we're root, 179 00:08:27,720 --> 00:08:29,010 and now, we're going to try this command again. 180 00:08:29,010 --> 00:08:33,663 So we're going to do cat /var/log .log. 181 00:08:37,110 --> 00:08:40,470 And now, in this example, when you first enter, 182 00:08:40,470 --> 00:08:42,090 that means the command was executed. 183 00:08:42,090 --> 00:08:45,210 If there's no feedback, you know it executed correctly, 184 00:08:45,210 --> 00:08:48,000 but for this example, the boot.log file is empty. 185 00:08:48,000 --> 00:08:51,030 So let's see which file is not empty, 186 00:08:51,030 --> 00:08:52,740 and now, we can see another boot log 187 00:08:52,740 --> 00:08:54,273 with a date stamp to it, 188 00:08:55,290 --> 00:08:58,570 boot log 20220517 189 00:09:01,153 --> 00:09:01,986 var 190 00:09:05,853 --> 00:09:06,936 log-20220517. 191 00:09:13,286 --> 00:09:14,460 And now, we can see the information 192 00:09:14,460 --> 00:09:16,310 that's associated with that boot log, 193 00:09:17,340 --> 00:09:18,720 and next, we want to exit out of this. 194 00:09:18,720 --> 00:09:21,690 Exit switches back to our regular user account. 195 00:09:21,690 --> 00:09:22,680 So the next thing we want to do 196 00:09:22,680 --> 00:09:25,200 is to leverage the tab completion command. 197 00:09:25,200 --> 00:09:27,570 We'll use the example by creating a long file name. 198 00:09:27,570 --> 00:09:29,046 So I'm going to name this 199 00:09:29,046 --> 00:09:30,713 thisisalongfilename. 200 00:09:35,070 --> 00:09:38,073 All right, we'll verify that created. 201 00:09:39,840 --> 00:09:42,340 Now, the tab command autocompletes 202 00:09:43,230 --> 00:09:46,233 any type of command or file name. 203 00:09:47,880 --> 00:09:49,230 So we're going to ls this out, 204 00:09:51,690 --> 00:09:53,547 and all we're going to have to press is the th, 205 00:09:53,547 --> 00:09:57,903 the first two characters of the file name and press tab, 206 00:09:59,010 --> 00:10:00,483 and it'll autocomplete. 207 00:10:03,300 --> 00:10:05,640 Again, this is just another convenient feature Linux 208 00:10:05,640 --> 00:10:08,880 which makes type of commands very efficient. 209 00:10:08,880 --> 00:10:12,120 Next thing we want to do is to use the history command, 210 00:10:12,120 --> 00:10:14,400 but we're going to tab that out, 211 00:10:14,400 --> 00:10:16,170 and the history command just shows you a list 212 00:10:16,170 --> 00:10:19,170 of all your most recent commands. 213 00:10:19,170 --> 00:10:22,530 So it'll be easier to jump back to a command. 214 00:10:22,530 --> 00:10:26,940 Maybe you forgot, but we also know that we can just arrow up 215 00:10:26,940 --> 00:10:29,733 and arrow down as well for those commands. 216 00:10:30,600 --> 00:10:31,710 So again, just want to note, 217 00:10:31,710 --> 00:10:34,018 tab completion works on commands, 218 00:10:34,018 --> 00:10:37,050 file names, and directories. 219 00:10:37,050 --> 00:10:40,650 Last thing want do is reboot the system. 220 00:10:40,650 --> 00:10:42,200 It's going to be a common feature. 221 00:10:48,514 --> 00:10:49,347 Okay. 222 00:10:57,030 --> 00:10:59,080 All right, we're back to our home screen. 223 00:11:00,150 --> 00:11:02,160 So thank you for walking through this lesson with me 224 00:11:02,160 --> 00:11:03,660 on entering shell commands 225 00:11:03,660 --> 00:11:05,460 and I'll see you in the next lesson.