View source for BASH/C2/Arithmetic-Comparison/English-timed

{| border=1 
|'''Time''' 
|'''Narration''' 

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|  00:01  
|  Welcome to the '''spoken tutorial''' on '''Arithmetic Comparison''' in '''BASH'''.

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|  00:07
| In this tutorial, we will learn:

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|  00:09
| * '''equal to (-eq)'''
 
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|  00:10
| * '''not equal to (-ne)'''
 
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|  00:12
|* '''less than (-lt)'''

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|  00:13
|* '''less than equal to (-le)'''

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|  00:15
|* '''greater than (-gt)''' and

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|  00:16
|* '''greater than equal to (-ge)''' '''commands'''.

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|  00:19
| We will do this with the help of some examples.

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| 00:23 
|  For this tutorial, I am using: 

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| 00:26 
| * '''Ubuntu Linux 12.04''' Operating System  

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| 00:30 
| *'''GNU BASH''' version '''4.1.10'''

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| 00:34 
| '''GNU Bash''' version '''4''' or above is recommended for practice.

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| 00:39
| I already have a working example of '''arithmetic operators'''. 

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| 00:43
| Let me switch to it.

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| 00:45
| I have named the file '''example1.sh'''.

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|  00:50  
|  Open a file in any '''editor''' of your choice and type the '''code''' as shown.

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|  00:56  
| You must be familiar how to do so, by now.

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| 01:00    
|   In this program, we will check whether a given file is empty or not.

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| 01:06  
|  Let me explain the '''code'''.

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| 01:08  
| This is the '''shebang line'''.

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|   01:10
|  First of all, “'''Enter filename”''' will be printed on the '''console.'''

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|  01:15
| '''read''' '''command''' reads  one line of data from the '''standard input.'''

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|  01:20 
|   This '''command''' is enclosed within '''backticks.'''

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|  01:24 
| '''Backtick''' has a very special meaning. 
 
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|  01:27 
| Everything you type between '''backtick''' is evaluated.

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|  01:32 
| '''cat''' command will display the content of the file.

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|  01:37 
| '''wc''' will print newline, word and byte counts for each file.

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|  01:43 
| '''- (hyphen) w''' will print the word count.

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|  01:47 
| What will happen is - 

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|  01:49 
| First the '''cat''' command will read the file. 

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|  01:53 
| This is the '''input file'''

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|  01:55 
|  which is then '''piped''' or sent to the '''wc''' command.

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|  02:00 
| So, this statement counts the words in a given file.

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|  02:05 
|  The '''output''' is stored in '''variable  x.'''

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|  02:08  
|   This is the '''if''' statement. 

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|  02:10  
| '''- (hyphen) eq''' command checks whether word count is equal to zero.

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|  02:16  
| If the condition is '''True,''' we will print a message '''"File has zero words”.'''

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|  02:22  
| '''"fi"''' is the end of first '''if''' condition.

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|  02:26
|   Here is another '''if''' condition.

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|  02:28
| Here, '''- (hyphen) ne''' command checks whether word count is not equal to zero.

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|  02:35
| If the condition is '''True,''' we print '''“File has so-and-so words”'''.

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|  02:40
| '''$x (dollar x)''' will give the word count.

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|  02:43
| This is the end of 2nd '''if '''condition.

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|  02:46
|  '''Save''' your '''program''' file.

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|  02:48
| Let us '''execute''' our program.

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|   02:51 
|  Open the '''terminal'''.

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|  02:53
|   First let's create a file '''list.txt'''.

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|  02:57
| Type: '''touch list.txt'''.

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| 03:01   
| Now, let's add a line in the file.

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| 03:04   
| Type:
'''echo within double quotes “How are you” after the double quotes greater than sign list.txt'''.

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|   03:13 
| Now let's make our '''script''' executable.

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| 03:16 
| Type:
'''chmod plus x example1 dot sh'''

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| 03:21 
| Now, type: '''dot slash example1.sh'''

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| 03:26 
| '''"Enter filename:" ''' is displayed.

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| 03:28 
| Type: '''list.txt'''

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| 03:31 
| The output is displayed as: '''"list.txt has 3 words"'''.

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|  03:36
|  Now let's learn about another set of '''operator'''s.

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| 03:40 
| Let me switch to another file.  

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| 03:43 
| This is '''example2.sh '''.

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| 03:46 
|  Please open a file in your '''editor''' and name it as "example2.sh".

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|   03:52
|  Now type the code as shown here, in your "example2.sh" file.

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| 03:58 
|  Let me explain the code.

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|  04:00
|  This program will check whether the word count is- 

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|  04:04
| * greater or less than one

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| 04:07
| * Between one and hundred or above hundred.

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|   04:11
|  We have our '''shebang line''' here.

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|  04:14
|   '''read ''' statement takes input as filename from the user.

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|  04:19
|  Here, '''- (hyphen) c''' command is used to print the '''byte''' counts.

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|  04:24
|  In the '''if statement''', '''- (hyphen) lt''' command checks whether word count is less than one.

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|  04:31
| If the condition is '''True''' then we print '''“No characters present in the file”.'''

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|  04:37
| '''"fi"''' ends the '''if condition.'''

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|  04:40
|   The next '''if statement''' contains a nested '''if statement.'''

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|  04:45
| First,  '''- (hyphen) gt''' command checks whether word count is greater than one.

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|  04:51
| If 'yes' then this '''echo statement ''' will be executed.

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| 04:56
|  There are multiple conditions within this '''if statement.'''

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| 05:01
| Here, in this '''if''':
* '''- (hyphen) ge '''command checks whether word count is greater than or equal to one and

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| 05:09
|* '''- (hyphen) le '''command checks whether word count is less than or equal to hundred.

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| 05:17
| If both the conditions are satisfied then it prints:

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| 05:21
| '''"Number of characters ranges between 1 and 100".'''

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| 05:25
| Please note that both '''conditions''' should be '''True''' to satisfy the entire '''if condition'''. 

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| 05:33
| This is because we have included ampersand in-between both the conditions. 

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| 05:39
| '''"fi"''' is the end of this '''if statement'''.

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|  05:43   
|  Then the next '''if statement '''will be evaluated.

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|  05:47   
| '''- (hyphen) gt '''command checks whether word count is greater than hundred.

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|  05:53   
| If the condition is satisfied, we print '''"Number of characters is above hundred".'''

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|  06:00   
| '''"fi" '''is the end of '''if statement.'''

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|  06:04
|  Here we end the 2nd '''if statement'''.

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|   06:07  
|  Now come back to our '''terminal'''.  

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|   06:10  
| Let us '''execute''' the program.

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|  06:13  
| '''chmod plus x example2 dot sh'''

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|  06:18
| '''dot slash example2 dot sh'''

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|  06:22
|  Type '''list.txt '''.

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|  06:25 
|   The '''output''' is displayed as '''"list.txt has more than one character"'''.

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| 06:31 
| '''"Number of characters ranges between one and hundred"'''.

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| 06:36 
|   Now, add or remove characters to the '''list.txt''' file.

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| 06:40 
| Then observe which '''if statement''' gets executed.

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|  06:46
|    This brings us to the end of this tutorial.

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|  06:49
| Let us summarize.

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| 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'''.

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|  07:03    
|  As an assignment, write a program to demonstrate the use of '''not equal to''' '''operator'''.

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|  07:09    
| Hint: '''- (hyphen) ne'''.

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|   07:12
|  Watch the video available at the link shown below.

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|   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

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|  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.

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|  07:51
| More information on this mission is available at the link shown below.

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|  07:56
| The script has been contributed by FOSSEE and spoken-tutorial team.

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|  08:02
| This is Ashwini Patil from IIT Bombay, signing off.

|-
|  08:06
| Thank you for joining.

|}