1 00:00:01,070 --> 00:00:08,900 To get the most from your Linux system, you need to understand environment variables and be adept adept 2 00:00:08,900 --> 00:00:13,430 at managing them for optimal performance, convenience and even stealth. 3 00:00:13,940 --> 00:00:19,730 So among the areas that the Linux newcomers find problematic, however, managing the user environment 4 00:00:19,730 --> 00:00:23,060 variables might be the most difficult to master. 5 00:00:23,600 --> 00:00:25,940 So technically, there are two types of variables. 6 00:00:26,600 --> 00:00:29,960 The first is shell, and the second is environment. 7 00:00:30,800 --> 00:00:37,010 So environment variables are system wide variables built into your system and interface that control 8 00:00:37,010 --> 00:00:44,840 the way your system looks, acts and feels the to the user and they are inherited by end charge shills 9 00:00:44,840 --> 00:00:45,710 or processors. 10 00:00:46,730 --> 00:00:54,500 Social variables, on the other hand, are typically listed listed in lowercase and are only valid in 11 00:00:54,500 --> 00:00:55,220 their shell. 12 00:00:55,250 --> 00:00:56,480 They are set in. 13 00:00:57,140 --> 00:01:04,130 So to avoid over explanation, I just, uh, cover some of the most basic and useful skills for environment 14 00:01:04,130 --> 00:01:10,460 and shell variables in this lectures and don't go too deeply into the differences between them. 15 00:01:11,240 --> 00:01:15,890 So variables are simple strings in key value pairs. 16 00:01:16,460 --> 00:01:28,100 So again, or generally, each pair will look like this, for example, key and value key here and add 17 00:01:28,100 --> 00:01:28,940 value here. 18 00:01:29,750 --> 00:01:30,200 So. 19 00:01:32,520 --> 00:01:42,750 In cases where there are multiple values, they will look like this is a value one value to and value 20 00:01:42,760 --> 00:01:44,610 three and vice versa here. 21 00:01:45,450 --> 00:01:53,790 So as with most things in Linux, if there are spaces in the value, it needs to be contained in a quotation 22 00:01:53,790 --> 00:01:54,870 marks here. 23 00:01:56,710 --> 00:01:57,410 Like that? 24 00:01:58,800 --> 00:02:00,290 While the fourth. 25 00:02:02,720 --> 00:02:03,140 So. 26 00:02:08,140 --> 00:02:12,640 So in in your environment, in your shell is your best shell. 27 00:02:12,910 --> 00:02:19,540 So each user, including ruled, has a different set of environment variables that determine how the 28 00:02:19,540 --> 00:02:21,280 system looks, acts and. 29 00:02:22,060 --> 00:02:28,570 So you can change the values for these variables to make your system work more efficiently. 30 00:02:28,810 --> 00:02:33,970 Tailor your work environment to best meet your individual needs and potentially cover your tracks if 31 00:02:33,970 --> 00:02:34,660 you need to. 32 00:02:35,740 --> 00:02:42,100 So leaving and modifying environment variables so you can be while your default environment variables 33 00:02:42,100 --> 00:02:49,060 by entering any V into your terminal from any directory like so here. 34 00:02:49,960 --> 00:02:54,010 So as you can see, there is a light environment variables here. 35 00:02:57,660 --> 00:03:03,660 So environment variables are always upper case, as you can see here. 36 00:03:05,190 --> 00:03:12,570 So, including shell variables, local variables and show functions such as any user defined variables 37 00:03:12,570 --> 00:03:20,050 and command aliases, some use a set common this command will list all environment variables. 38 00:03:20,520 --> 00:03:28,410 Um, on environment variables unique to your system, which is the most cases will give you an output 39 00:03:28,410 --> 00:03:33,660 so long you won't be able to view it, uh, on a single screen here. 40 00:03:34,230 --> 00:03:35,430 So you can see here. 41 00:03:36,360 --> 00:03:40,410 We have so many environment variables here. 42 00:03:43,680 --> 00:03:51,660 As you can see here, we can see, because it's so many here, so, uh, we can do like that, sit here. 43 00:03:52,620 --> 00:03:53,070 Said. 44 00:03:54,260 --> 00:03:55,880 And more here. 45 00:03:57,220 --> 00:04:00,100 Now we can see like that by pressing enter. 46 00:04:00,430 --> 00:04:02,040 We can see a sequential. 47 00:04:02,400 --> 00:04:10,990 So let's see more more and, uh, press in one time control and save or exit or quit here. 48 00:04:11,980 --> 00:04:17,740 So now the last three of us here, as you can see here, feel, uh, will fill up on a screen line by 49 00:04:17,740 --> 00:04:18,880 line and then stop. 50 00:04:19,330 --> 00:04:26,940 Uh, when you press enter like that, uh, or space or, uh, spin in space and you will see more here. 51 00:04:28,160 --> 00:04:36,020 Uh, so, uh, taking you to the next variable so you can scroll through pressing or holding, enter 52 00:04:36,020 --> 00:04:36,560 like that. 53 00:04:37,190 --> 00:04:37,580 So. 54 00:04:39,490 --> 00:04:46,990 As you might recall, from previous chapters and elections, whenever you you use, the more common 55 00:04:46,990 --> 00:04:59,380 for output you can enter key it to or exit and return command to like that or control plus easier. 56 00:05:00,190 --> 00:05:03,490 So filtering for particular variables? 57 00:05:03,910 --> 00:05:06,160 Let me, uh, see here. 58 00:05:06,170 --> 00:05:14,440 So, uh, I'll talk to you using sent, uh, with more gifts, more, uh, manageable results than working 59 00:05:14,440 --> 00:05:20,950 through the whole chunk of variable names you get with this sit along like that. 60 00:05:22,030 --> 00:05:23,020 Uh, so. 61 00:05:24,740 --> 00:05:28,580 It can still be a rather tedious if you are looking for a particular variable. 62 00:05:28,880 --> 00:05:35,540 Instead, you can use the filtering command grant, um to find your variable of interest. 63 00:05:35,960 --> 00:05:39,350 So let's use the variable his size as an example. 64 00:05:39,770 --> 00:05:46,070 So this variable contains his size on this variable contains the maximum number of comments you were. 65 00:05:46,070 --> 00:05:48,470 Common history of a file was stored. 66 00:05:49,190 --> 00:05:58,310 So his size is the maximum and number of commands your command history file will start to his commands 67 00:05:58,550 --> 00:06:06,070 or any was previously typed into your command prompt in the session and can be recalled with your up 68 00:06:06,080 --> 00:06:10,760 here, up and down, uh, keywords like that. 69 00:06:13,440 --> 00:06:19,710 So you're not at his size, doesn't store the comments themselves, just a number of them that can be 70 00:06:19,720 --> 00:06:29,580 stored so popular, sit here said, Oh crap, actually cramp his size. 71 00:06:29,970 --> 00:06:30,300 Yeah. 72 00:06:30,980 --> 00:06:33,870 Well, as you can see, his size is 1000. 73 00:06:34,200 --> 00:06:39,840 As you can see, the common finds the variable, his size, and this place is its value. 74 00:06:40,230 --> 00:06:45,570 The default value of this variable is probably set to one thousand here, as you can see on your system, 75 00:06:45,570 --> 00:06:45,900 too. 76 00:06:46,230 --> 00:06:52,080 So this indicates the terminal this storage would last 1000 commands by default.