WEBVTT 00:00.140 --> 00:01.190 Hello friends. 00:01.190 --> 00:04.040 Welcome again to a new section of this course series. 00:04.040 --> 00:08.870 In this section we are going to see the fundamentals of Linux Shell scripting. 00:08.870 --> 00:14.420 This section is an update to this course for the year 2025. 00:14.450 --> 00:22.820 Okay, this section will be different as compared to other sections because this section consists of 00:22.820 --> 00:23.570 articles. 00:23.600 --> 00:32.030 Okay, all the fundamental topics are covered in the form of articles, and this video is really important 00:32.030 --> 00:36.260 for you to understand the basics of Linux shell scripting. 00:36.290 --> 00:36.770 Okay. 00:36.800 --> 00:42.740 There are two videos in which I am going to explain everything practically. 00:42.740 --> 00:49.880 Once you go through these videos, then understanding of the articles will become easier for you. 00:50.030 --> 00:53.270 Okay, so this is the first video. 00:53.270 --> 01:00.620 And in this video we are going to see how to declare variables, how to take user input and how to execute 01:00.620 --> 01:01.940 your script. 01:02.010 --> 01:02.400 Okay. 01:02.430 --> 01:03.630 So let's see. 01:04.920 --> 01:08.340 So as you can see here, these are the articles. 01:08.370 --> 01:09.030 Okay. 01:09.060 --> 01:15.210 In the first article we have covered what is Linux Shell scripting and its uses. 01:15.240 --> 01:15.870 Okay. 01:15.900 --> 01:21.690 When you read this article you will understand everything very easily. 01:21.690 --> 01:23.940 You don't need anyone's help. 01:23.970 --> 01:24.420 Okay. 01:24.450 --> 01:27.780 And this is applicable to all the articles. 01:27.780 --> 01:33.840 But before that, it is very important for you to understand the basics. 01:33.840 --> 01:38.910 Once you understand the basics, then you will understand the rest. 01:38.940 --> 01:39.570 Okay. 01:39.600 --> 01:46.350 And if you already know the computer programming, then you don't need to take these videos. 01:46.350 --> 01:50.070 You will understand every article very easily. 01:50.100 --> 01:55.110 Okay, so first of all let's understand what is a Linux shell script? 01:55.140 --> 02:00.540 Linux shell scripting refers to writing a series of commands for shell to execute. 02:00.570 --> 02:08.170 Means we write commands in a script file and we can execute those commands, okay. 02:08.200 --> 02:12.940 We can write multiple commands in a single shell script file. 02:12.970 --> 02:16.300 We don't need to type those commands again and again on the terminal. 02:16.330 --> 02:23.530 By writing multiple commands in a single shell script file, we can execute it again and again. 02:23.800 --> 02:28.000 Okay, after this, let's see the basic structure of Linux shell script. 02:28.000 --> 02:32.800 So as you can see here, this is the basic Linux shell script. 02:32.800 --> 02:35.890 It consists of different parts okay. 02:35.920 --> 02:38.860 At the beginning you need to include the shebang line. 02:38.890 --> 02:42.250 This shebang line consists of different parts. 02:42.250 --> 02:50.170 The first part is hash and negation symbol, and the next part is the path to the bash shell, which 02:50.170 --> 02:52.600 is present in the root bin directory. 02:52.630 --> 02:59.230 Okay, so here we want to use the bash shell okay for executing our script. 02:59.230 --> 03:02.440 It is also called as the born again shell okay. 03:02.470 --> 03:08.790 There are different types of shell present in the Linux, and you can use according to your choice. 03:08.820 --> 03:12.090 Okay, you gonna learn about it in the next article? 03:12.090 --> 03:17.520 Suppose I want to use the conch shell to execute this script. 03:17.520 --> 03:26.670 Then I just need to replace this bash with the ksh and our script will be executed with conch shell. 03:26.700 --> 03:32.670 Okay, so you need to include the shebang line according to the type of shell that you want to use in 03:32.670 --> 03:34.890 your script after this. 03:34.920 --> 03:37.830 This part here is called as the comments. 03:37.830 --> 03:42.990 So the comment is used to describe the purpose of your script or code. 03:42.990 --> 03:47.700 So it says that this is a simple shell script example. 03:47.760 --> 03:51.660 So it is explaining the purpose of this shell script. 03:51.660 --> 03:54.840 Then here it says define a variable. 03:54.840 --> 03:58.560 So here it shows the purpose of this line of code. 03:58.560 --> 04:02.160 So here variable is defined okay. 04:02.160 --> 04:05.470 So this is the purpose of this comment code. 04:05.470 --> 04:10.390 So comment are defined with this hash followed by the text. 04:10.420 --> 04:15.670 Okay so this is the basic structure which consists of shebang line then. 04:15.670 --> 04:16.450 Comments. 04:16.480 --> 04:18.430 Comments are not necessary. 04:18.430 --> 04:23.290 If you don't want to include the comment then you can exclude that part. 04:23.290 --> 04:28.330 Then your commands, then variables and then control structures. 04:28.450 --> 04:28.870 Okay. 04:28.900 --> 04:33.310 So this is the basic structure of a Linux shell script. 04:33.340 --> 04:33.850 Okay. 04:33.880 --> 04:37.090 After this let's see what are variables. 04:37.300 --> 04:37.810 Okay. 04:37.840 --> 04:40.240 Variables are used to store the data. 04:40.270 --> 04:41.080 Okay. 04:41.320 --> 04:45.370 If you know the programming then you will understand what are variables. 04:45.370 --> 04:48.160 So how to declare a variable. 04:48.160 --> 04:51.910 So to declare a variable you need to type the variable name. 04:51.910 --> 05:00.910 Then use assignment operator and assign the value here included inside the double quote okay as described 05:00.910 --> 05:01.600 here. 05:02.020 --> 05:07.160 And after declaring the variable, it is important for you to access the variable. 05:07.160 --> 05:14.870 So to access the variable, you need to add the dollar sign before your variable name that you declared. 05:14.900 --> 05:21.530 Okay, so as you can see in this code, a greeting variable is declared and assign the value. 05:21.560 --> 05:22.190 Hello. 05:22.220 --> 05:25.760 Okay so this is a string or characters. 05:25.760 --> 05:32.000 Then the next variable is name and assign the value Alice okay. 05:33.140 --> 05:40.580 And we are printing those values to the screen with the help of echo command okay. 05:40.610 --> 05:46.430 And we are accessing those values or these variables with the help of dollar symbol. 05:46.430 --> 05:54.200 You need to add the dollar symbol before your variable name and after that taking user input. 05:54.200 --> 05:59.450 So to take user input you need to use the command read okay. 05:59.480 --> 06:05.240 With read command, you can take any user input and then print it to the computer screen. 06:05.240 --> 06:07.800 Or you can perform your operation. 06:07.830 --> 06:08.190 Okay. 06:08.220 --> 06:11.640 It depends upon your script need. 06:11.670 --> 06:15.990 Okay, so we have learned that the basic structure of a Linux shell script. 06:16.020 --> 06:19.860 How to declare a variable and how to take user input. 06:19.890 --> 06:22.470 So this is just the theoretical part. 06:22.500 --> 06:24.720 So let's do it practically. 06:26.430 --> 06:29.430 So first of all let's create a script file. 06:29.430 --> 06:35.100 So I want to go with VI editor and type the name of the script. 06:35.100 --> 06:41.880 So I want to name it as let's say name dot bash. 06:41.880 --> 06:47.400 You need to add the same extension according to your shell that you want to use. 06:47.400 --> 06:50.340 So I want to use the bash shell. 06:50.340 --> 06:55.560 That's why I'm going to add the extension bash and hit enter. 06:55.590 --> 07:01.470 Okay, after getting inside let's get into insert mode by pressing I. 07:03.090 --> 07:06.300 So first of all you need to add the shebang line. 07:06.300 --> 07:08.960 So let's add the shebang line first. 07:11.540 --> 07:13.760 Bin forward. 07:13.760 --> 07:16.190 Slash bash. 07:16.700 --> 07:18.770 Okay, this is our shebang line. 07:18.890 --> 07:21.650 Okay, after this, let's declare our variable. 07:21.650 --> 07:25.910 So I want to declare a variable name. 07:26.000 --> 07:28.250 Variables are case sensitive. 07:28.280 --> 07:28.970 Okay. 07:29.090 --> 07:36.260 Once you declare the variable name as name like this, you cannot access the name variable with capital 07:36.290 --> 07:36.890 N. 07:38.090 --> 07:39.500 Like this. 07:39.920 --> 07:40.550 Okay. 07:40.550 --> 07:41.900 You cannot access this. 07:41.900 --> 07:49.070 You need to use the same spelling or the letter combination, whether it is small letter or capital 07:49.070 --> 07:49.790 letter. 07:50.060 --> 07:50.480 Okay. 07:50.480 --> 07:51.470 So. 07:53.870 --> 07:56.390 Let's assign a value here. 07:59.690 --> 08:01.010 This is my name. 08:01.160 --> 08:08.330 And after this I want to declare another variable address equal to. 08:08.340 --> 08:08.880 hear. 08:08.880 --> 08:12.660 I want to assign imaginary address. 08:15.870 --> 08:19.350 Host number 14 or 24. 08:22.170 --> 08:24.540 Mira Road, Pune. 08:25.110 --> 08:25.740 Okay. 08:26.310 --> 08:32.310 After this, let's print these values to the computer screen. 08:32.310 --> 08:35.040 So let's use the command echo. 08:35.070 --> 08:40.200 The purpose of echo command is to print the information to the computer screen. 08:40.230 --> 08:40.770 Okay. 08:40.770 --> 08:45.930 It prints a text or your variable data to the computer screen. 08:45.930 --> 08:50.760 So now, uh, let's use the dollar symbol. 08:50.790 --> 08:51.180 Okay. 08:51.210 --> 08:53.100 Now we are accessing the variables. 08:53.100 --> 08:55.440 So you need to use the dollar symbol. 08:55.440 --> 08:58.260 And then the variable name as it is. 08:58.290 --> 08:58.710 Okay. 08:58.740 --> 09:00.300 The way you declare the variable. 09:00.300 --> 09:04.650 So name and double quote okay. 09:05.070 --> 09:06.120 After this. 09:06.150 --> 09:09.490 Let's access the second Variable. 09:09.910 --> 09:16.900 Use dollar symbol and variable name like this. 09:18.760 --> 09:26.110 Now press Escape ctrl Shift colon wq and hit enter. 09:26.350 --> 09:29.800 Now our code is written to our script. 09:30.190 --> 09:31.660 Let's do ls. 09:31.660 --> 09:36.370 And as you can see name dot bash file is created. 09:38.710 --> 09:41.230 Now let's see the contents of our file. 09:41.260 --> 09:44.380 Cat name dot bash. 09:44.380 --> 09:47.350 And as you can see this is our data. 09:47.350 --> 09:51.790 So now it's time to execute our script file. 09:51.790 --> 09:56.410 So to execute our script file we need to make it executable. 09:56.410 --> 10:07.090 So let's make it executable with chmod add plus x and name dot bash and hit enter. 10:07.180 --> 10:09.670 Now our file is executable. 10:09.670 --> 10:17.300 And to execute the script, you need to use dot operator and forward slash and the file name. 10:17.300 --> 10:21.680 So let's add name dot bash and hit enter. 10:21.980 --> 10:25.490 Okay we got an error here at line number eight. 10:25.490 --> 10:27.650 So let's debug the script. 10:29.990 --> 10:31.640 Name dot bash. 10:34.130 --> 10:39.080 Okay here we need to add a space after echo command. 10:41.570 --> 10:44.150 Let's execute it again. 10:50.000 --> 10:52.430 Now it is executed successfully. 10:54.560 --> 10:55.940 Let's do it again. 10:55.940 --> 11:02.840 And as you can see it shows the name and address we have assigned to our variables. 11:03.230 --> 11:03.710 Okay. 11:03.710 --> 11:08.780 So I think you have understand how shell script work basically. 11:09.260 --> 11:12.390 So first we declare the variable name and address. 11:12.420 --> 11:18.930 Assign the values or data and print it to the computer screen with the help of echo command. 11:18.960 --> 11:27.390 So this is how you can declare a variable and assign data and print the data to the computer screen. 11:27.420 --> 11:31.590 Okay, after this let's see how to take the user input. 11:33.780 --> 11:39.720 So let's create another file v input dot dash. 11:41.640 --> 11:46.290 So in this example I want to take user input. 11:46.290 --> 11:50.010 So first of all include the shebang line. 11:50.640 --> 11:53.250 Bin bash. 11:54.300 --> 12:01.650 After this with equal command print the message to the computer screen. 12:02.460 --> 12:04.320 Enter your name. 12:04.500 --> 12:05.250 Okay. 12:05.520 --> 12:11.250 This time we're gonna get the user name from command line. 12:11.280 --> 12:11.670 Okay. 12:11.780 --> 12:16.580 so after this you need to type the command read. 12:16.610 --> 12:17.240 Read. 12:17.240 --> 12:20.690 Command will take the user input. 12:20.720 --> 12:21.080 Okay. 12:21.110 --> 12:22.820 With the help of a variable. 12:22.820 --> 12:25.580 So you need to declare a variable here. 12:25.670 --> 12:26.240 Okay. 12:26.240 --> 12:28.850 So the variable is name. 12:29.780 --> 12:35.120 After that display the entered name to the computer screen. 12:36.830 --> 12:37.130 Type. 12:37.130 --> 12:42.860 The message name is equal to our variable name. 12:42.860 --> 12:48.650 So use dollar symbol and the variable name and add the double quote. 12:48.770 --> 12:53.120 Okay after this press escape control shift colon. 12:53.570 --> 12:56.210 Now make the script executable. 12:56.210 --> 12:58.070 So first clear the screen. 12:58.220 --> 13:04.340 Let's see our file cat input dot bash. 13:04.370 --> 13:04.730 Okay. 13:04.760 --> 13:07.160 This is our data or our script code. 13:07.250 --> 13:09.440 Now make it executable. 13:10.760 --> 13:16.800 So just type the command Chmod plus x okay. 13:16.920 --> 13:19.260 And execute the code. 13:19.260 --> 13:23.730 So just type dot forward slash and hit enter. 13:24.120 --> 13:27.750 So as you can see the message is printed at the beginning. 13:27.780 --> 13:28.800 Enter your name. 13:28.800 --> 13:32.190 And now it is waiting for our input. 13:32.190 --> 13:38.250 So I'm going to enter my name here Prashant okay. 13:38.280 --> 13:44.580 Now this data is stored to the variable name with the help of read command. 13:44.580 --> 13:53.310 And when I hit enter, it prints that data to the computer screen with the help of echo command. 13:53.310 --> 13:58.320 So this is how you can take the user input okay. 13:58.350 --> 14:01.110 And print it to the computer screen. 14:01.140 --> 14:05.940 Or you can perform different operations with user input. 14:05.970 --> 14:09.840 It always depends on your script need. 14:09.840 --> 14:14.970 So this is how you can perform these basic operations inside Linux shell scripting.