BASH/C2/Arithmetic-Comparison/English-timed

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: - (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.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Ranjana, Sandhya.np14