1 00:00:01,290 --> 00:00:08,670 Do remember how I told you that many system administrators do mistake on the first line of the script. 2 00:00:08,700 --> 00:00:12,500 So let's talk about siobhán and why it is important. 3 00:00:12,750 --> 00:00:22,070 But first let's create a new directory called Bash. 4 00:00:22,280 --> 00:00:24,780 You know we can create file I don't. 5 00:00:24,840 --> 00:00:25,760 Sh h. 6 00:00:29,230 --> 00:00:35,250 And on the first line just type Shabak followed by bin bash 7 00:00:41,470 --> 00:00:44,020 for text we want to display on the screen output. 8 00:00:44,060 --> 00:00:45,840 We use echo command. 9 00:00:45,940 --> 00:00:53,220 Basically everything you open after keyboard Echo will be displayed on the output of the script. 10 00:00:53,590 --> 00:00:56,030 As will the current directory. 11 00:00:56,470 --> 00:01:06,350 And if we type on the echo it will print empty line. 12 00:01:06,770 --> 00:01:11,450 Now some command about output of P.W. the command 13 00:01:18,220 --> 00:01:27,530 and of course we can finish script by using BWT safe changes and we do our editor using ls command. 14 00:01:27,580 --> 00:01:31,610 I will check what permissions are set for file and we just created. 15 00:01:31,920 --> 00:01:36,560 I will change permissions by granting exec permission for everyone. 16 00:01:36,660 --> 00:01:42,080 And of course using US you can check that everything is set up correctly. 17 00:01:45,810 --> 00:01:51,530 Now I can run the script and it's working perfectly. 18 00:01:51,570 --> 00:01:54,440 So now let's talk about the siobhán. 19 00:01:54,870 --> 00:01:58,680 I will firstly display script content using got commom 20 00:02:01,420 --> 00:02:09,680 But the question is why it is called siobhán the first character is called Shop. 21 00:02:09,740 --> 00:02:13,830 You can for example notice this symbol in famous programming language. 22 00:02:13,880 --> 00:02:21,770 C-Sharp the second character exclamation mark is in the slang called Ben. 23 00:02:22,090 --> 00:02:22,900 Why. 24 00:02:23,260 --> 00:02:31,650 Because whenever divorce Benke is used especially in comics it is followed by exclamation mark. 25 00:02:31,670 --> 00:02:42,540 Now put those two characters together sharp and bank and vote you get is Shaban many people using shebang. 26 00:02:42,730 --> 00:02:46,770 But it means still the same characters. 27 00:02:47,250 --> 00:02:49,780 Now everything that follows siobhán. 28 00:02:49,960 --> 00:02:58,280 In our case sledged been slashed bash means that this interpreter is invoked to ram our script basically. 29 00:02:58,300 --> 00:03:04,780 In other words it is called sledged been slash and bash to ram our script. 30 00:03:05,260 --> 00:03:09,730 And this is how it looks like what is executed behind the scene. 31 00:03:09,850 --> 00:03:19,590 Bin bash dot slash in the name of our script as the dot slash represents the current directory. 32 00:03:19,750 --> 00:03:27,110 Basically it means the expression been Bash and name of our script. 33 00:03:28,240 --> 00:03:29,570 Here's just one note. 34 00:03:29,740 --> 00:03:33,490 You don't need at all to use Shabangu line. 35 00:03:33,610 --> 00:03:40,570 If you vote call your script each time with an interpreter as we did now with bin bash but in a real 36 00:03:40,570 --> 00:03:43,120 world this wouldn't happen. 37 00:03:44,290 --> 00:03:51,040 As no one prefers to run the script by prepending interpreter a name before name of the script. 38 00:03:51,040 --> 00:03:58,080 It is always better to specify it on the shebang line in your script. 39 00:03:58,140 --> 00:04:06,520 So now let's create a copy of our script and do some experiment. 40 00:04:07,460 --> 00:04:09,190 I will create that I do. 41 00:04:09,250 --> 00:04:15,440 S H I said copy and now open your script 42 00:04:20,360 --> 00:04:27,090 and change interpretor from bin bash to bin and 43 00:04:33,030 --> 00:04:36,010 save changes and it does editor 44 00:04:39,530 --> 00:04:41,600 now from descript 45 00:04:45,330 --> 00:04:55,030 see that there is no output type ls command and where it is dry. 46 00:04:55,060 --> 00:05:01,940 That as age descript was removed as if you basically did the following. 47 00:05:02,270 --> 00:05:10,160 We called our n common with one argument Our screen name. 48 00:05:10,490 --> 00:05:19,590 So that led to removing our script. 49 00:05:19,900 --> 00:05:21,250 Let's create a screen 50 00:05:24,310 --> 00:05:34,860 and we can see now that we have only tried to do it as a file so let's rename it to try Daut s h. 51 00:05:36,790 --> 00:05:39,460 Now open right as I age in anti-Torah 52 00:05:42,780 --> 00:05:52,220 and change interpretor from bin bash to something that doesn't exist for example been Swash. 53 00:05:52,920 --> 00:05:56,910 And we can make some common here by putting sharp character 54 00:06:03,090 --> 00:06:11,550 save your changes and go back to term you know if we now around our script we get better interpreter 55 00:06:11,550 --> 00:06:15,820 Noddy's and it's correct because men isolation doesn't exist. 56 00:06:16,080 --> 00:06:19,260 I have made it up now open again. 57 00:06:19,290 --> 00:06:30,470 Our script we can firstly remove our common and change interpreter to be in a stage 58 00:06:34,200 --> 00:06:36,590 now save changes and then run the script 59 00:06:40,990 --> 00:06:48,280 many administrators use been a stage and they sometimes fring that it is pointing been beshe and they 60 00:06:48,280 --> 00:06:53,280 are right in most cases been as age points to been beshe. 61 00:06:53,800 --> 00:06:58,820 But in my case you can see that it points to Desch. 62 00:06:59,070 --> 00:07:06,750 It is in my case because you want to change default system shall be as age to Desch. 63 00:07:06,780 --> 00:07:14,070 So remember when you will deploy your script to another machine always check that interpreter you have 64 00:07:14,070 --> 00:07:18,950 used for script is also present on another machine. 65 00:07:19,170 --> 00:07:20,970 Otherwise you are risking. 66 00:07:21,120 --> 00:07:24,030 That script won't work as expected.