Difference between revisions of "BASH/C2/Arithmetic-Comparison/English-timed"
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| 00:09 | | 00:09 | ||
| − | | * '''equal to''' | + | | * '''equal to (-eq)''' |
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| 00:10 | | 00:10 | ||
| − | | * '''not equal to''' | + | | * '''not equal to (-ne)''' |
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| 00:12 | | 00:12 | ||
| − | |* '''less than''' | + | |* '''less than (-lt)''' |
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| 00:13 | | 00:13 | ||
| − | |* '''less than equal to''' | + | |* '''less than equal to (-le)''' |
|- | |- | ||
| 00:15 | | 00:15 | ||
| − | |* '''greater than''' and | + | |* '''greater than (-gt)''' and |
|- | |- | ||
| 00:16 | | 00:16 | ||
| − | |* '''greater than equal to''' '''commands'''. | + | |* '''greater than equal to (-ge)''' '''commands'''. |
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| 02:00 | | 02:00 | ||
| − | | So, this | + | | So, this statement counts the words in a given file. |
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| 02:16 | | 02:16 | ||
| − | | If the condition is '''True,''' we will print a message ''' | + | | If the condition is '''True,''' we will print a message '''"File has zero words”.''' |
|- | |- | ||
| 02:22 | | 02:22 | ||
| − | | '''fi''' is the end of first '''if''' condition. | + | | '''"fi"''' is the end of first '''if''' condition. |
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| 02:40 | | 02:40 | ||
| − | | '''$ (dollar | + | | '''$x (dollar x)''' will give the word count. |
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| 02:48 | | 02:48 | ||
| − | | Let us '''execute''' our | + | | Let us '''execute''' our program. |
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| 03:26 | | 03:26 | ||
| − | | '''Enter filename: ''' is displayed. | + | | '''"Enter filename:" ''' is displayed. |
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| 03:28 | | 03:28 | ||
| − | | Type: | + | | Type: '''list.txt''' |
| − | '''list.txt''' | + | |
|- | |- | ||
| 03:31 | | 03:31 | ||
| − | | The output is displayed as: '''list.txt has 3 words'''. | + | | The output is displayed as: '''"list.txt has 3 words"'''. |
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| 03:46 | | 03:46 | ||
| − | | Please open a file in your '''editor''' and name it as | + | | Please open a file in your '''editor''' and name it as "example2.sh". |
|- | |- | ||
| 03:52 | | 03:52 | ||
| − | | Now type the code as shown here in your | + | | Now type the code as shown here, in your "example2.sh" file. |
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| 04:37 | | 04:37 | ||
| − | | '''fi''' ends the '''if condition.''' | + | | '''"fi"''' ends the '''if condition.''' |
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| 04:45 | | 04:45 | ||
| − | | First, | + | | First, '''- (hyphen) gt''' command checks whether word count is greater than one. |
|- | |- | ||
| 04:51 | | 04:51 | ||
| − | | If yes | + | | If 'yes' then this '''echo statement ''' will be executed. |
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| 05:21 | | 05:21 | ||
| − | | '''Number of characters ranges between 1 and 100.''' | + | | '''"Number of characters ranges between 1 and 100".''' |
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| 05:25 | | 05:25 | ||
| − | | Please note that both '''conditions''' should be | + | | Please note that both '''conditions''' should be '''True''' to satisfy the entire '''if condition'''. |
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| 05:39 | | 05:39 | ||
| − | | '''fi''' is the end of this '''if statement'''. | + | | '''"fi"''' is the end of this '''if statement'''. |
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| 05:53 | | 05:53 | ||
| − | | If the condition is satisfied, we print '''Number of characters is above hundred.''' | + | | If the condition is satisfied, we print '''"Number of characters is above hundred".''' |
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| 06:00 | | 06:00 | ||
| − | | '''fi '''is the end of '''if statement.''' | + | | '''"fi" '''is the end of '''if statement.''' |
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| 06:25 | | 06:25 | ||
| − | | The '''output''' is displayed as '''list.txt has more than one character'''. | + | | The '''output''' is displayed as '''"list.txt has more than one character"'''. |
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| 06:31 | | 06:31 | ||
| − | | '''Number of characters ranges between one and hundred'''. | + | | '''"Number of characters ranges between one and hundred"'''. |
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| 07:03 | | 07:03 | ||
| − | | As an assignment, write a program to demonstrate the use of '''not equal to''' operator. | + | | As an assignment, write a program to demonstrate the use of '''not equal to''' '''operator'''. |
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| 07:09 | | 07:09 | ||
| − | | Hint: '''- (hyphen) ne''' | + | | Hint: '''- (hyphen) ne'''. |
|- | |- | ||
Revision as of 11:49, 13 July 2015
Title of script: Arithmetic comparison in BASH
Author: Ashwini Patil
Keywords: video tutorial, Bash shell, -eq, -ne, -gt, -ge, -lt, -le
| 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) |
| 00:10 | * not equal to (-ne) |
| 00:12 | * less than (-lt) |
| 00:13 | * less than equal to (-le) |
| 00:15 | * greater than (-gt) and |
| 00:16 | * greater 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:
|
| 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:
|
| 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. |
