1 00:00:03,540 --> 00:00:08,160 At the beginning of the course you started learning about the absolute necessities when it comes to 2 00:00:08,160 --> 00:00:09,380 shell scripting. 3 00:00:09,390 --> 00:00:13,830 You found out that it really doesn't matter what the final name of the shellscript is or what extension 4 00:00:13,830 --> 00:00:15,450 it has if any. 5 00:00:15,450 --> 00:00:20,480 The most important thing is its permissions and specifically the execute permission. 6 00:00:20,550 --> 00:00:25,530 You learn how to add executable permissions to your scripts with the chmod command. 7 00:00:25,740 --> 00:00:30,240 Once you started writing shell scripts you learned the importance of using a sharp bang on the very 8 00:00:30,270 --> 00:00:32,070 first line of your script. 9 00:00:32,100 --> 00:00:37,560 You also learned how to insert comments in your script you quickly started using variables to store 10 00:00:37,560 --> 00:00:39,660 values in your script. 11 00:00:39,660 --> 00:00:46,300 You use the echo shell built in to generate standard output including displaying the contents of variables. 12 00:00:46,440 --> 00:00:50,880 You learned that using single quotes around a string makes it a literal string. 13 00:00:50,880 --> 00:00:56,280 That means everything in the single quotes is displayed exactly as it appears in your shell script. 14 00:00:56,990 --> 00:00:59,600 What do you want to allow for variable expansion. 15 00:00:59,600 --> 00:01:02,040 You learned to use double quotes. 16 00:01:02,420 --> 00:01:08,540 You learned how to use the type command to determine if a command is a shell builtin or a Linux command 17 00:01:08,870 --> 00:01:10,310 to get help on a shell built in. 18 00:01:10,310 --> 00:01:18,570 You use the help Shaad built in command for Linux commands you learn how to use and read man pages. 19 00:01:18,680 --> 00:01:23,960 You also learned how to take advantage of some of the shell variables that you get for free when using 20 00:01:23,960 --> 00:01:25,130 bash. 21 00:01:25,130 --> 00:01:30,040 Some of the variables you've used included hostname random and you ID. 22 00:01:30,290 --> 00:01:35,840 We talked about command substitution and how the dollar sign parentheses syntax is the current favorite 23 00:01:35,840 --> 00:01:41,840 way to perform that command substitution while surrounding a command and back ticks is the older syntax 24 00:01:42,050 --> 00:01:45,120 that you may still encounter from time to time. 25 00:01:45,200 --> 00:01:50,060 You assign the output of commands to variables using this method as well as using the output of those 26 00:01:50,060 --> 00:01:53,560 commands directly or as part of other commands. 27 00:01:54,430 --> 00:01:59,380 Once you started creating scripts that had multiple steps and requirements you were introduced to the 28 00:01:59,380 --> 00:02:05,500 concept of pseudo coding which is simply a high level description of what your script will do. 29 00:02:05,500 --> 00:02:11,410 You then went back over your steps and filled in the exact commands and details required to make those 30 00:02:11,410 --> 00:02:14,040 steps function correctly. 31 00:02:14,090 --> 00:02:17,030 You also learn how to use an IF statement. 32 00:02:17,060 --> 00:02:23,240 We talked about how you can use expressions in operator supported by the test built in between the double 33 00:02:23,240 --> 00:02:25,450 brackets of the if statement. 34 00:02:25,460 --> 00:02:31,250 We also talked about the older syntax of using single brackets for conditional expressions. 35 00:02:31,250 --> 00:02:34,640 The use of the if statement brought us to exit statuses. 36 00:02:34,640 --> 00:02:39,800 That's because the if statement was checking to see if an expression was successful or not before it 37 00:02:39,830 --> 00:02:42,320 executed the appropriate code block. 38 00:02:43,010 --> 00:02:49,750 When a command completes successfully it returns an exit status of 0 when it doesn't it returns a non 39 00:02:49,750 --> 00:02:51,610 zero exit status. 40 00:02:51,620 --> 00:02:56,930 You learned how to control the exit status of your scripts by using the exit shell built in. 41 00:02:56,930 --> 00:03:02,390 You also learn how to check the exit status of the most recent command by examining the contents of 42 00:03:02,390 --> 00:03:03,700 the variable dollar sign. 43 00:03:03,700 --> 00:03:05,320 Question mark. 44 00:03:05,320 --> 00:03:08,840 You use the if statement to perform some sanity checking. 45 00:03:08,870 --> 00:03:11,320 Users don't always behave the way you want them to. 46 00:03:11,390 --> 00:03:17,180 And systems are not always configured exactly the same if something is required for your script to execute 47 00:03:17,180 --> 00:03:18,170 successfully. 48 00:03:18,170 --> 00:03:23,870 You learn that you have to check for it when you started using multiple options to various commands. 49 00:03:23,870 --> 00:03:29,870 We talked about how you can combine multiple single character options following just one hyphen for 50 00:03:29,870 --> 00:03:30,710 most options. 51 00:03:30,710 --> 00:03:36,080 The order doesn't matter so you can execute the same command in multiple ways and still get the exact 52 00:03:36,110 --> 00:03:37,230 same result. 53 00:03:37,940 --> 00:03:43,250 Also many commands give you the option of using a single character option or a longer version of that 54 00:03:43,250 --> 00:03:49,200 option when there are two forms of the same options such as dash and or dash dash name. 55 00:03:49,220 --> 00:03:52,290 You only need to use one of the forms. 56 00:03:52,460 --> 00:03:57,980 By the way all the variations of the ID command you see here on your screen are equivalent and produce 57 00:03:57,980 --> 00:04:05,960 the exact same output next to learn how to use the read shell builtin in order to capture standard input 58 00:04:06,140 --> 00:04:08,300 and store it in a variable. 59 00:04:08,300 --> 00:04:13,110 You then moved on to creating random data that you could use for account passwords. 60 00:04:13,160 --> 00:04:17,730 One way you did this was by taking advantage of the random shell variable. 61 00:04:17,810 --> 00:04:23,030 Another method you use to was to take the output of the data command and run it through a cryptographic 62 00:04:23,030 --> 00:04:27,870 hash function you then started working with positional parameters. 63 00:04:27,870 --> 00:04:32,970 You learn that arguments are what are supplied to your script and that parameters are what you use to 64 00:04:32,970 --> 00:04:35,630 store those arguments inside of your script. 65 00:04:35,640 --> 00:04:38,920 Not only did you learn about dollar $0 1 and so on. 66 00:04:39,030 --> 00:04:45,450 You learned about a few special parameters such as Dollar Sign asterisk dollar sign and sign and dollar 67 00:04:45,450 --> 00:04:51,060 sign pound sign because you can't always anticipate the number of arguments you use or may supply to 68 00:04:51,060 --> 00:04:51,930 your script. 69 00:04:51,960 --> 00:04:56,390 You use the for loop to loop through each of the positional parameters. 70 00:04:56,760 --> 00:05:01,320 You also learn how to create while loops while the test returns true. 71 00:05:01,380 --> 00:05:04,530 The code block between do and done will be executed. 72 00:05:04,530 --> 00:05:09,830 This means that during a while loop you'll want to change the thing being tested for in some way so 73 00:05:09,840 --> 00:05:15,250 that the condition eventually evaluates to false or you'll end up in an infinite loop. 74 00:05:15,600 --> 00:05:21,840 Finally you learn how to fully manipulate standard input standard output and standard error by using 75 00:05:21,930 --> 00:05:23,980 i o redirection. 76 00:05:24,030 --> 00:05:28,660 One of the first forms of IO redirection you used came in the form of a pipe. 77 00:05:28,860 --> 00:05:34,760 You took the standard output of one command and piped it as the standard input into another command. 78 00:05:34,950 --> 00:05:40,230 You were able to start with some output and by making small changes to a series of pipes you were able 79 00:05:40,230 --> 00:05:42,970 to put it in the exact format that you wanted. 80 00:05:43,860 --> 00:05:50,250 Next you covered IO redirection to and from files you learned that using a single greater than sign 81 00:05:50,250 --> 00:05:56,430 when redirecting will create a new file or overwrite the existing contents of a file if it already exists 82 00:05:57,120 --> 00:05:59,670 in order to append to a file without overwriting it. 83 00:05:59,670 --> 00:06:06,470 You use the double greater than sign syntax you redirected the contents of a file as standard input 84 00:06:06,650 --> 00:06:09,870 into a command by using the less than sign. 85 00:06:09,920 --> 00:06:15,740 You also learn how to send standard error to a file as well as how to send both standard output and 86 00:06:15,740 --> 00:06:17,770 standard error to a file. 87 00:06:18,110 --> 00:06:24,170 You continued working with pipes and learn how to send both standard output and standard error as standard 88 00:06:24,170 --> 00:06:32,280 input through a pipe by using the pipe ampersand syntax in order to conform to the convention of sending 89 00:06:32,280 --> 00:06:38,230 error messages to standard error you learn how to redirect standard output to standard error. 90 00:06:38,310 --> 00:06:42,830 You also learn how to discard output by sending it to the nolde device. 91 00:06:42,840 --> 00:06:47,440 I hope you realize how far you've come in a relatively short period of time. 92 00:06:47,670 --> 00:06:52,770 At this point you could easily go off and write all kinds of useful shell scripts. 93 00:06:52,770 --> 00:06:57,420 You know how to control the flow of your scripts you know about input and output redirection. 94 00:06:57,420 --> 00:07:03,840 You know how to perform loops you understand many shell scripting conventions and on and on. 95 00:07:03,840 --> 00:07:09,380 In short if you've completed this course you are so far ahead of most shellscript yours. 96 00:07:09,390 --> 00:07:12,510 However I encourage you to keep learning and practicing. 97 00:07:12,540 --> 00:07:18,450 Of course one of the best ways to do that is to use your skills to perform some real world work that 98 00:07:18,450 --> 00:07:19,890 you need to get done. 99 00:07:19,890 --> 00:07:25,980 Pick something that you need to automate or make easier be it something you do at home or at work. 100 00:07:25,980 --> 00:07:29,150 Finally I want to congratulate you on completing this course. 101 00:07:29,280 --> 00:07:33,190 It's so easy to start something yet so hard to finish it. 102 00:07:33,360 --> 00:07:34,350 If you've made it this far. 103 00:07:34,350 --> 00:07:37,850 Know that you're one of the few who see things through to the end. 104 00:07:37,860 --> 00:07:40,010 For that I really respect you. 105 00:07:40,050 --> 00:07:43,600 I wish you the best and I hope to see you in another one of my courses soon.