BASH/C2/Case-statement/English-timed

Time	Narration
00:01	Dear friends, welcome to the spoken tutorial on Case statement in Bash.
00:07	In this tutorial, we will learn: Importance of case statement Syntax of case statement with an example.
00:17	To follow this tutorial, you should have knowledge on basics of Shell Scripting.
00:23	If not, for relevant tutorials, please visit our website which is as shown.
00:29	For this tutorial, I am using: Ubuntu Linux 12.04 Operating System and GNU BASH version 4.1.10
00:39	Please note, GNU Bash version 4 or above is recommended to practice this tutorial.
00:47	The Bash shell has two forms of conditional statements. if statement and case statement.
00:56	Case statement can be alternately used in place of if-else statement.
01:03	The case statement is preferred when there are many items to select from.
01:09	It is usually used to implement menus in a script.
01:14	Let us see the syntax.
01:15	case space $(dollar) VARIABLE space in match_1 close round brackets space commands and semicolon twice
01:27	match_n close round bracket space commands and semicolon twice asterisk close round bracket space command_to_execute_by_default and semicolon twice esac.
01:45	The VARIABLE is compared to match_1.
01:48	If it does not match, it moves on to the next case which is match_n.
01:54	It will check if any one of these strings matches VARIABLE.
02:01	If yes, then all the commands until the double semicolon (;;) are executed.
02:07	If neither match VARIABLE, the commands associated with the asterisk are executed.
02:14	It is the default case condition because the asterisk will match all strings.
02:21	esac marks the end of case block.
02:26	Let us understand case statement with an example.
02:32	I have already typed the program. So, I will open the file case.sh.
02:38	The program prints a warning message when the disk space reaches a certain limit.
02:45	This is the shebang line.
02:47	The location of bash is different in other Linux flavors like CentOS, RedHat etc.
02:55	Previously used /bin/bash points directly to the binary file.
03:01	env used here, abstracts the true location where bash is located.
03:07	This shebang line improves the portability of the script on any GNU/Linux system.
03:16	df -(hyphen)h displays disk space usage in human readable form.
03:22	The output is piped to sort -rk5 which sorts the fifth column in reverse order.
03:31	The output is then passed to awk 'FNR == 2 {print $5}'
03:38	which extracts the fifth field of the second line.
03:43	Eventually, the output is passed to cut -(hyphen)d “% -(hyphen)f1” to strip out % sign.
03:55	This is the first line of case statement.
03:59	Here, we compare the space between 0 and 69.
04:04	If match is found, it prints "Everything is OK”
04:08	Next, it compares the space between 70 and 89 or from 91 to 98;
04:17	If match is found, it prints “Clean out. There's a partition that is $(dollar)space % full.”
04:27	Here, it compares the space with 99.
04:30	If match is found, it prints “Hurry. There's a partition at $(Dollar) space %!”
04:39	This is the default case condition because the asterisk will match all strings.
04:45	And this is the end of case statement.
04:48	Now go to the terminal to make the file executable.
04:52	Type: chmod plus x case dot sh
04:57	Type: dot slash case dot sh
05:02	Everything is OK. Note that the output will vary depending on your system disk space.
05:10	In my machine, as match is found between 0 and 69, it prints Everything is OK.
05:18	Check the message printed on your machine.
05:20	You will be able to understand which case statement was executed.
05:27	This brings us to the end of this tutorial. Let us summarize.
05:31	In this tutorial, we learnt: Importance of case statement Syntax of case statement with the disc-space example.
05:41	As an assignment:
05:42	Write a menu driven program for mathematical calculation;
05:47	It should take user inputs a and b;
05:51	It should ask for mathematical operator (plus +, minus -, division / and multiplication *). Do the calculation, print the output.
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06:48	The script has been contributed by FOSSEE and spoken-tutorial team.
06:53	This is Ashwini from IIT Bombay. Thank you for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14