Difference between revisions of "BASH/C2/Case-statement/English-timed"

| Dear friends, Welcome to the spoken tutorial on '''Case statement in Bash.'''

| In this tutorial, we will learn Importance of '''case statement''' Syntax of '''case statement''' with an Example

| To follow this tutorial, you should have knowledge on Basics of '''Shell Scripting'''.

|If not, for relevant tutorials please visit our website which is as shown.

| For this tutorial I am using ''' Ubuntu Linux''' 12.04''' Operating System''' and '''GNU BASH''' version 4.1.10

|  The '''Bash '''shell has two forms of conditional statements.  These are the '''if statement''' and the '''case statement. '''

|'''Case statement '''can be alternately used in place of '''if-else statement'''

|The '''case statement''' is preferred when there are many items to select from.

|It is usually used to implement '''menus''' in a script.

|Let us see the syntax.

 

|'''case space $(dollar)VARIABLE space in''' '''match_1''' close round brackets space '''commands''' and semicolon twice

|'''match_n''' close round bracket space '''commands''' and semicolon twice '''asterisk''' close round bracket space command_to_execute_by_default''' and semicolon twice '''esac'''

|It will check if any one of these strings matches '''VARIABLE. '''

|If yes, then all the commands until the double''' semicolon (;;) '''are executed.

| I have already typed the program.So, I will open the file''' case.sh'''  

|The location of '''bash '''is different in other '''Linux''' flavours like '''CentOS, RedHat etc.'''

|Previously used '''/bin/bash '''points directly to the''' binary file'''.

|This '''shebang '''line improves the portability of the script on any '''GNU/Linux''' system.

| '''df -(hyphen)h displays disk space''' usage in human readable form.

|The output is piped to '''sort -rk5''', which sorts the fifth column in reverse order.

|The output is then passed to '''awk 'FNR == 2 {print $5}''''  

|which extracts the fifth field of the second line.

|Eventually, the output is passed to '''cut -(hyphen)d “% -(hyphen)f1” '''to strip out '''% sign.'''

|If match is found, it prints “'''Everything is OK”'''

| Next, it compares the '''space''' between 70 and 89 or from 91 to 98;

| This is the default case condition because the '''asterisk '''will match all strings.

| Now go to the''' terminal,'''to make the file'' ''executable.

|Type''' chmod space plus x space case dot sh '''

|Type '''dot slash case dot sh'''

| '''Everything is OK.'''Note that the output will vary depending on your system diskspace.

| In my machine, as match is found between 0 and 69, it prints '''Everything is OK.'''

|You will be able to understand which '''case statement''' was executed.

|This brings us to the end of this tutorial. Let us summarize.

|In this tutorial we learnt, Importance of''' case statement''' Syntax of '''case statement''' With the disc space example

| As an assignment.

 

|05:42

|Write a menu driven program for mathematical calculation

| It should take user inputs '''a '''and '''b'''

| It should ask for mathematical opertator(plus +, minus -, division / and multiplication *)Do the calculation Print the output

| 06:01

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|This is Ashwini from IIT Bombay.Thank you for joining.