Difference between revisions of "BASH/C2/Arithmetic-Comparison/English-timed"

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|  Welcome to the '''spoken tutorial''' on '''Arithmetic Comparison''' in '''BASH'''
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Revision as of 16:25, 3 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
00:10 * not equal to
00:12 * less than
00:13 * less than equal to
00:15 * greater than and
00:16 * greater than equal to 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 $ (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, the - (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