1 00:00:01,180 --> 00:00:06,730 Welcome to this lecture we are going to learn how to shorten the if statement. 2 00:00:06,940 --> 00:00:13,720 But firstly I will check what follows I have present here and if I am using Basho 3 00:00:16,200 --> 00:00:23,030 So if you want to write a statement we do it in following way. 4 00:00:23,640 --> 00:00:30,270 If then some condition then the statement for case of one condition is true. 5 00:00:31,050 --> 00:00:42,410 And then after our skeeball statement if condition is not true and we are ending with F 6 00:00:45,400 --> 00:00:48,940 and here we are testing if File hello. 7 00:00:49,090 --> 00:00:52,050 No text exists and it exists. 8 00:00:54,130 --> 00:00:58,960 I will change the file name to be sure that descriptive works great. 9 00:00:58,960 --> 00:01:01,370 It works fine. 10 00:01:01,430 --> 00:01:10,180 Now if you want to shorten if statement we are starting with square brackets then instead of give or 11 00:01:10,240 --> 00:01:17,960 and then we are using double ampersand and basically telling if that condition is true due to stuff 12 00:01:18,050 --> 00:01:22,940 after double ampersand and has it is working. 13 00:01:23,550 --> 00:01:28,390 If we use instead of double understandable pipe we are telling. 14 00:01:28,530 --> 00:01:34,230 If that condition is not true do the stuff after double type. 15 00:01:34,630 --> 00:01:39,670 So as a result we got no output as condition is true. 16 00:01:39,990 --> 00:01:43,190 If we change file name to some which doesn't exist 17 00:01:47,260 --> 00:01:51,870 we receive correct message doesn't exits. 18 00:01:52,250 --> 00:01:59,500 Let's make it more interesting and use in a one line double ampersand and double bind together. 19 00:01:59,530 --> 00:02:09,580 Many people think that the pipes here representing our statement but that's not true even it does look 20 00:02:09,850 --> 00:02:12,030 like the script is working correctly. 21 00:02:13,320 --> 00:02:18,760 And it is working correctly even for non existing file. 22 00:02:18,780 --> 00:02:21,250 We will see. 23 00:02:21,550 --> 00:02:31,540 So how it is working then we are starting with square brackets with condition that condition is returning 24 00:02:31,600 --> 00:02:33,060 exit status. 25 00:02:33,340 --> 00:02:37,070 Then we have a double ampersand followed by statement. 26 00:02:37,180 --> 00:02:41,680 That statement is executed only if exit status is zero. 27 00:02:43,060 --> 00:02:50,800 And then we have double pipe followed by statement and that statement is executed only if exit status 28 00:02:50,890 --> 00:03:01,420 is not zero but if statement after double ampersand is executed it is executed with some exit status 29 00:03:02,110 --> 00:03:06,700 which can be different from initial condition letter requested. 30 00:03:06,760 --> 00:03:17,430 If file exists so to realize what is going on would be best to change statement after that but ampersand 31 00:03:17,670 --> 00:03:21,790 into some command which will exit with non-zero status. 32 00:03:21,810 --> 00:03:30,590 For example being to not reachable IP address. 33 00:03:30,680 --> 00:03:33,620 And now if we executed this 34 00:03:42,380 --> 00:03:48,250 we see death being C'mon was clearly executed. 35 00:03:48,650 --> 00:03:58,400 But we also see message doesn't exist which is the best proven that there is no Alice statement at all. 36 00:03:58,400 --> 00:04:07,190 So once more file test condition and the route exit status of 0 and because of dead the pink Gaumont 37 00:04:07,280 --> 00:04:15,000 after double ampersand was executed being a command ended with exits that was the one. 38 00:04:15,290 --> 00:04:16,940 And because of death. 39 00:04:17,270 --> 00:04:25,980 But after double pipe was executed as that part is executed when exit status is not zero. 40 00:04:27,890 --> 00:04:34,190 We can use short if statement not only for final test operands we can't test anything. 41 00:04:34,220 --> 00:04:37,050 For example exits tattles. 42 00:04:37,190 --> 00:04:41,540 So if exit status is zero we can put in 43 00:04:44,410 --> 00:04:44,770 command. 44 00:04:44,770 --> 00:04:46,490 OK. 45 00:04:47,400 --> 00:04:52,880 And otherwise we will print something went wrong. 46 00:04:54,160 --> 00:04:58,770 That's basically Yukako month cannot be exited with non-zero exit status. 47 00:04:58,840 --> 00:05:03,580 We are using cadabra pipes here as our statement. 48 00:05:03,800 --> 00:05:13,840 And we can test if it is working on something which will exit with non-zeros those. 49 00:05:13,850 --> 00:05:18,110 So for example in our case bank being some reachable address 50 00:05:32,210 --> 00:05:35,220 and see that something went wrong. 51 00:05:35,270 --> 00:05:35,690 Great. 52 00:05:35,720 --> 00:05:37,390 It is working. 53 00:05:37,710 --> 00:05:41,800 Now it's time to create some small simple script 54 00:05:44,690 --> 00:05:51,560 so I'm creating file secret as I age and starting with siobhán. 55 00:05:52,490 --> 00:05:55,490 Then I ask guz for age 56 00:05:59,870 --> 00:06:05,520 and then really do variable called 8. 57 00:06:06,140 --> 00:06:14,810 Now we can ask if age is less than for example funding. 58 00:06:15,880 --> 00:06:17,650 And in that case we will print. 59 00:06:17,770 --> 00:06:24,100 You are not allowed to see the secret. 60 00:06:24,760 --> 00:06:32,350 You are not allowed to see the secret 61 00:06:35,270 --> 00:06:46,880 otherwise brain print Rock'em but it would be great to exit script when Duzer is displayed you are not 62 00:06:46,940 --> 00:06:48,070 allowed to see the secret. 63 00:06:48,110 --> 00:06:51,960 So we put Exit 1 after that message. 64 00:06:52,790 --> 00:06:54,960 And if you want to do multiple commands. 65 00:06:54,980 --> 00:07:03,260 After double ampersand or double pipe we need to put it into parenthesis or Carol-Lee brackets parentheses 66 00:07:03,410 --> 00:07:06,570 will create sub shell that those commands are. 67 00:07:06,980 --> 00:07:10,430 Which is not always good as you will see later. 68 00:07:11,900 --> 00:07:24,090 And at the end we will print that secret so we can print secret is that there is no secret save to file 69 00:07:31,520 --> 00:07:31,940 ground. 70 00:07:31,990 --> 00:07:33,090 Is it with permission 71 00:07:38,230 --> 00:07:38,920 and then. 72 00:07:40,560 --> 00:07:44,760 If you specify age 25 it works. 73 00:07:44,950 --> 00:07:54,820 Bhakt when I put age for example 15 something went wrong. 74 00:07:54,910 --> 00:07:56,820 I see all messages printed. 75 00:07:57,040 --> 00:07:58,760 So what has happened here. 76 00:07:59,880 --> 00:08:09,330 So I will open a script to show you that as I told you when we use parentheses comments are from in 77 00:08:09,330 --> 00:08:09,970 subcellar. 78 00:08:10,020 --> 00:08:18,060 Basically it means in another show an exit command only exited that shell and because thats actual written 79 00:08:18,340 --> 00:08:19,790 exit's that was the one. 80 00:08:19,800 --> 00:08:28,530 We also see the message of l.com because statements after double pipes are executed if exit status is 81 00:08:28,710 --> 00:08:29,890 not zero. 82 00:08:31,380 --> 00:08:38,670 So now let's change the script and instead of parentheses we will use Gardley brackets. 83 00:08:38,670 --> 00:08:49,500 Here it is important that after first first Gardley break it to have space and before that last curly 84 00:08:49,500 --> 00:08:51,710 break it to have a semicolon 85 00:08:55,790 --> 00:08:58,100 Now you can save descript 86 00:09:06,000 --> 00:09:06,650 and you can Adani 87 00:09:09,490 --> 00:09:11,630 for age 25. 88 00:09:12,510 --> 00:09:13,940 It works fine. 89 00:09:14,390 --> 00:09:23,430 And for age for example then also fine b c you are not allowed to see this secret great.