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Time Narration
00:01 Welcome to the spoken tutorial on Command line arguments and Quoting in BASH.
00:08 In this tutorial, we will learn about:
00:11 Command line Arguments and
00:13 Quoting.
00:15 To follow this tutorial, you should be familiar with the Linux Operating System.
00:20 If not, for relevant tutorials please visit our website which is as shown.
00:26 For this tutorial, I am using:
00:29 Ubuntu Linux 12.04 OS
00:33 GNU Bash version 4.1.10
00:37 GNU Bash version 4 or above is recommended for practice.
00:43 Shell script can accept arguments from the command line.
00:46 An argument is passed to a program being called.
00:52 Any number of arguments can be passed to a program.
00:57 Let us open the terminal by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
01:06 I have already written the code in the file named
01:12 On the terminal, let me open this file by typing-
01:16 gedit space space ampersand sign(&).
01:23 We use the ampersand to free up the prompt.
01:27 Now, press Enter.
01:30 The text editor is opened.
01:33 Let me explain the code now.
01:36 This is the shebang line.
01:39 This line will print the zeroth argument.
01:43 Here, $0 (Dollar zero) will print the name of the shell script.
01:48 This, in turn, means that the zeroth argument is the name of the program itself.
01:55 Let us execute the program and see.
01:59 Switch to the terminal.
02:01 First, make the file executable by typing:
02:05 chmod space plus x space
02:12 Press Enter.
02:14 Now, type: dot slash
02:18 Press Enter.The output is displayed as: Zeroth argument is
02:26 Now, come back to our editor and type the three lines as shown here.
02:33 $1 (Dollar one) represents the first argument passed to the program from the command line.
02:40 $2 (Dollar two) represents the second argument passed to the program
02:44 and $3 (Dollar three) represents the third argument.
02:48 Now, click on Save.Let us execute the program and see.
02:52 Press the up-arrow key, press Enter.
02:57 We see that the zeroth argument is printed
03:00 but the first, second and third arguments are blank.
03:05 This is because the command line arguments are given during execution.
03:11 Hence, press the up-arrow key and type: sunday monday and tuesday
03:18 Press Enter.
03:21 You can see that the first, second and third arguments are sunday monday and tuesday.
03:28 Now switch back to our editor. Press Enter.
03:33 Now, type the line as shown here.
03:37 $12 (Dollar twelve) represents the twelfth argument.
03:41 To write an argument greater than 9, we need to use curly brackets.
03:46 Else, bash will only take the argument of the integer in the ten's place
03:53 and you will not get expected output.
03:57 Now click on Save.
03:59 Let us execute the program.
04:01 Switch to the terminal.
04:04 Let me clear the prompt.
04:07 Now we need to give 12 or 13 arguments to the program.
04:12 Hence, type: dot slash space 1 to 13. Now press Enter.
04:23 You can see that the 12th argument is 12.
04:27 Come back to our editor
04:30 and type the line as shown here.
04:34 $# (Dollar hash) gives the total number of arguments that have been passed to a program.
04:40 Now click on Save.
04:43 Let us execute.Switch to the terminal.
04:46 Let us execute. Press the up-arrow key and press Enter.
04:52 We can see that the total arguments are 13.
04:57 Now switch to the editor.
05:00 Press Enter and type the lines as shown here.
05:04 $* (Dollar asterisk) will print all the arguments on a single line.
05:10 We will test this with the help of a simple for loop.
05:14 We will analyze this for loop at the time of execution.
05:18 Now, click on Save. Switch to the terminal.
05:22 Let me clear the prompt.
05:26 Now, let us type: dot slash space sunday monday and tuesday.
05:35 Press Enter.
05:38 You can see that the total number of arguments are 3 as we have passed 3 arguments to our program.
05:46 As already said, $* will print all the arguments on a single line.
05:54 And this is the output for the for loop.
05:57 We see that all the arguments are printed on the single line.
06:02 Now, move back to our program and type the lines as shown here.
06:09 $@ (Dollar at) will also print all the arguments.
06:13 However, this time each argument will be printed on separate line.
06:20 This is another for loop which will print each argument in a separate line.
06:26 Let us see how. Click on Save.
06:29 Switch to the terminal.
06:32 Press the up-arrow key.
06:34 Press Enter. You can see the difference now.
06:39 These are the arguments printed by $@.
06:43 $@ prints each argument on separate line.
06:47 This is the output for the 2nd for loop.
06:52 Now let's move on to quoting in BASH.
06:55 Switch to the slides.
06:57 There are three types of quotes:
06:59 Double quote Single quote
07:02 Backslash.Double quote substitutes the value of variables and commands.
07:09 Example echo “Username is $USER”.
07:13 It displays the username of the system.
07:17 Switch to the Terminal.
07:20 Let me clear the prompt.
07:23 Now, type: echo space within double quotes Username space is dollar USER in capitals.
07:34 Press Enter. The username of the system is printed.
07:39 The output will vary according to your system.
07:42 Now move back to slides.
07:46 Single quotes preserves the literal meaning of each character of a given string.
07:53 It is used to turn off special meaning of all characters.
07:58 Switch to the Terminal.
08:01 Type: echo space within single quote Username is dollar USER in capital.
08:10 Press Enter.
08:12 The output is Username is $USER.
08:16 In this example, it prints all the characters which appear within the single quotes.
08:23 It does not substitute the value of variable $USER.
08:28 Switch back to our slides.
08:31 Backslash removes the special meaning from a single character.
08:37 It is used as an escape character in BASH.
08:42 Switch to the Terminal.
08:44 Now, type: echo space within double quote Username is backslash dollar USER (in capital).
08:55 Since we have given double quotes, we expect the echo command to display the username.
09:02 Let's try this command, so press Enter.
09:06 The output is Username is $USER.
09:10 In this example, the backslash removes the special meaning of (Dollar) '$' symbol.
09:16 $USER is just treated as a string without any special functionality.
09:22 This brings us to the end of this tutorial.
09:25 Switch back to our slides.
09:27 Let us summarize. In this tutorial, we learnt:
09:31 Command line arguments
09:33 Functionality of double quote, single quote and backslash.
09:39 Watch the video available at the link shown below.
09:42 It summarizes the Spoken-Tutorial project.
09:45 If you do not have good bandwidth, you can download and watch it.
09:51 The Spoken Tutorial Project team: Conducts workshops using spoken tutorials.
09:56 Gives certificates to those who pass an online test.
10:00 For more details, please write to
10:07 Spoken Tutorial Project is a part of the "Talk to a Teacher" project.
10:10 It is supported by the National Mission on Education through ICT, MHRD, Government of India.

More information on this mission is available at:

10:24 The script has been contributed by FOSSEE and spoken-tutorial team.
10:30 And this is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

Gaurav, Pratik kamble, Sandhya.np14