BASH/C2/Arithmetic-Comparison/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on Arithmetic Comparison in BASH. |
| 00:07 | In this tutorial, we will learn: |
| 00:09 | equal to (-eq) not equal to (-ne) |
| 00:12 | less than (-lt)'less than equal to (-le)' |
| 00:15 | greater than (-gt) andgreater than equal to (-ge) commands. |
| 00:19 | We will do this with the help of some examples. |
| 00:23 | For this tutorial, I am using: |
| 00:26 | Ubuntu Linux 12.04 Operating System |
| 00:30 | GNU BASH version 4.1.10 |
| 00:34 | GNU Bash version 4 or above is recommended for practice. |
| 00:39 | I already have a working example of arithmetic operators. |
| 00:43 | Let me switch to it. |
| 00:45 | I have named the file example1.sh. |
| 00:50 | Open a file in any editor of your choice and type the code as shown. |
| 00:56 | You must be familiar how to do so, by now. |
| 01:00 | In this program, we will check whether a given file is empty or not. |
| 01:06 | Let me explain the code. |
| 01:08 | This is the shebang line. |
| 01:10 | First of all, “Enter filename” will be printed on the console. |
| 01:15 | read command reads one line of data from the standard input. |
| 01:20 | This command is enclosed within backticks. |
| 01:24 | Backtick has a very special meaning. |
| 01:27 | Everything you type between backtick is evaluated. |
| 01:32 | cat command will display the content of the file. |
| 01:37 | wc will print newline, word and byte counts for each file. |
| 01:43 | - (hyphen) w will print the word count. |
| 01:47 | What will happen is - |
| 01:49 | First the cat command will read the file. |
| 01:53 | This is the input file |
| 01:55 | which is then piped or sent to the wc command. |
| 02:00 | So, this statement counts the words in a given file. |
| 02:05 | The output is stored in variable x. |
| 02:08 | This is the if statement. |
| 02:10 | - (hyphen) eq command checks whether word count is equal to zero. |
| 02:16 | If the condition is True, we will print a message "File has zero words”. |
| 02:22 | "fi" is the end of first if condition. |
| 02:26 | Here is another if condition. |
| 02:28 | Here, - (hyphen) ne command checks whether word count is not equal to zero. |
| 02:35 | If the condition is True, we print “File has so-and-so words”. |
| 02:40 | $x (dollar x) will give the word count. |
| 02:43 | This is the end of 2nd if condition. |
| 02:46 | Save your program file. |
| 02:48 | Let us execute our program. |
| 02:51 | Open the terminal. |
| 02:53 | First let's create a file list.txt. |
| 02:57 | Type: touch list.txt. |
| 03:01 | Now, let's add a line in the file. |
| 03:04 | Type:
echo within double quotes “How are you” after the double quotes greater than sign list.txt. |
| 03:13 | Now let's make our script executable. |
| 03:16 | Type:
chmod plus x example1 dot sh |
| 03:21 | Now, type: dot slash example1.sh |
| 03:26 | "Enter filename:" is displayed. |
| 03:28 | Type: list.txt |
| 03:31 | The output is displayed as: "list.txt has 3 words". |
| 03:36 | Now let's learn about another set of operators. |
| 03:40 | Let me switch to another file. |
| 03:43 | This is example2.sh . |
| 03:46 | Please open a file in your editor and name it as "example2.sh". |
| 03:52 | Now type the code as shown here, in your "example2.sh" file. |
| 03:58 | Let me explain the code. |
| 04:00 | This program will check whether the word count is- |
| 04:04 | greater or less than one |
| 04:07 | Between one and hundred or above hundred. |
| 04:11 | We have our shebang line here. |
| 04:14 | read statement takes input as filename from the user. |
| 04:19 | Here, - (hyphen) c command is used to print the byte counts. |
| 04:24 | In the if statement, - (hyphen) lt command checks whether word count is less than one. |
| 04:31 | If the condition is True then we print “No characters present in the file”. |
| 04:37 | "fi" ends the if condition. |
| 04:40 | The next if statement contains a nested if statement. |
| 04:45 | First, - (hyphen) gt command checks whether word count is greater than one. |
| 04:51 | If 'yes' then this echo statement will be executed. |
| 04:56 | There are multiple conditions within this if statement. |
| 05:01 | Here, in this if:
- (hyphen) ge command checks whether word count is greater than or equal to one and |
| 05:09 | - (hyphen) le command checks whether word count is less than or equal to hundred. |
| 05:17 | If both the conditions are satisfied then it prints: |
| 05:21 | "Number of characters ranges between 1 and 100". |
| 05:25 | Please note that both conditions should be True to satisfy the entire if condition. |
| 05:33 | This is because we have included ampersand in-between both the conditions. |
| 05:39 | "fi" is the end of this if statement. |
| 05:43 | Then the next if statement will be evaluated. |
| 05:47 | - (hyphen) gt command checks whether word count is greater than hundred. |
| 05:53 | If the condition is satisfied, we print "Number of characters is above hundred". |
| 06:00 | "fi" is the end of if statement. |
| 06:04 | Here we end the 2nd if statement. |
| 06:07 | Now come back to our terminal. |
| 06:10 | Let us execute the program. |
| 06:13 | chmod plus x example2 dot sh |
| 06:18 | dot slash example2 dot sh |
| 06:22 | Type list.txt . |
| 06:25 | The output is displayed as "list.txt has more than one character". |
| 06:31 | "Number of characters ranges between one and hundred". |
| 06:36 | Now, add or remove characters to the list.txt file. |
| 06:40 | Then observe which if statement gets executed. |
| 06:46 | This brings us to the end of this tutorial. |
| 06:49 | Let us summarize. |
| 06:51 | In this tutorial we learnt:
equal to not equal to less than less than equal to greater than and greater than equal to commands. |
| 07:03 | As an assignment, write a program to demonstrate the use of not equal to operator. |
| 07:09 | Hint: - (hyphen) ne. |
| 07:12 | Watch the video available at the link shown below. |
| 07:15 | It summarizes the Spoken-Tutorial project. |
| 07:18 | If you do not have good bandwidth, you can download and watch it. |
| 07:23 | The Spoken Tutorial Project team: |
| 07:25 | Conducts workshops using spoken tutorials. |
| 07:28 | Gives certificates to those who pass an online test. |
| 07:32 | For more details, please write to contact@spoken-tutorial.org |
| 07:40 | Spoken Tutorial project is a part of the Talk to a Teacher project. |
| 07:43 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 07:51 | More information on this mission is available at the link shown below. |
| 07:56 | The script has been contributed by FOSSEE and spoken-tutorial team. |
| 08:02 | This is Ashwini Patil from IIT Bombay, signing off. |
| 08:06 | Thank you for joining. |
