Difference between revisions of "BASH/C2/Case-statement/English-timed"
From Script | Spoken-Tutorial
PoojaMoolya (Talk | contribs) |
|||
| Line 30: | Line 30: | ||
|- | |- | ||
| 00:47 | | 00:47 | ||
| − | | The '''Bash '''shell has two forms of conditional statements. | + | | The '''Bash '''shell has two forms of conditional statements. '''if statement''' and '''case statement. ''' |
|- | |- | ||
| Line 90: | Line 90: | ||
|- | |- | ||
| 02:32 | | 02:32 | ||
| − | | I have already typed the program.So, I will open the file''' case.sh''' | + | | I have already typed the program.So, I will open the file '''case.sh''' |
|- | |- | ||
| Line 106: | Line 106: | ||
|- | |- | ||
|02:55 | |02:55 | ||
| − | |Previously used '''/bin/bash '''points directly to the''' binary file'''. | + | |Previously used '''/bin/bash''' points directly to the''' binary file'''. |
|- | |- | ||
| Line 146: | Line 146: | ||
|- | |- | ||
|04:04 | |04:04 | ||
| − | |If match is found, it prints | + | |If match is found, it prints '''"Everything is OK”''' |
|- | |- | ||
| Line 174: | Line 174: | ||
|- | |- | ||
| 04:48 | | 04:48 | ||
| − | | Now go to the''' terminal,'''to make the file | + | | Now go to the''' terminal,''' to make the file executable. |
|- | |- | ||
| Line 206: | Line 206: | ||
|- | |- | ||
|05:31 | |05:31 | ||
| − | |In this tutorial we learnt, Importance of''' case statement''' Syntax of '''case statement''' With the disc space example | + | |In this tutorial we learnt, Importance of''' case statement''', Syntax of '''case statement''', With the disc space example |
|- | |- | ||
| Line 222: | Line 222: | ||
|- | |- | ||
|05:51 | |05:51 | ||
| − | | It should ask for mathematical opertator(plus +, minus -, division / and multiplication *)Do the calculation Print the output | + | | It should ask for mathematical opertator (plus +, minus -, division / and multiplication *). Do the calculation, Print the output |
|- | |- | ||
| − | | 06: | + | | 06:02 |
| Watch the video available at the link shown below | | Watch the video available at the link shown below | ||
Revision as of 12:50, 8 December 2014
| 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 flavours 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 space plus x space 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 diskspace. |
| 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 opertator (plus +, minus -, division / and multiplication *). Do the calculation, Print the output |
| 06:02 | Watch the video available at the link shown below |
| 06:06 | It summarises the Spoken Tutorial project |
| 06:08 | If you do not have good bandwidth, you can download and watch it |
| 06:14 | The Spoken Tutorial Project Team |
| 06:16 | Conducts workshops using spoken tutorials .Gives certificates to those who pass an online test |
| 06:23 | For more details, please write to contact@spoken-tutorial.org |
| 06:31 | Spoken Tutorial Project is a part of the Talk to a Teacher project |
| 06:35 | It is supported by the National Mission on Education through ICT, MHRD, Government of India More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro |
| 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. |
