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Bash Scripting Exercise

To be performed on your Linux machine

Exercise 1: Every bash script usually begins with a Shebang (#!) – It is used to specify the absolute path of the bash.

Example: #!/bin/bash

Create a folder in your home folder called BASH. cd to BASH.

Gedit a file: mybash1.sh. Add the above shebang and save. Change the mode of mybash1.sh to an executable. Recall our Linux exercise on changing modes.

 

Exercise 2: Add this code in mybash1.sh. Do not just copy. Type it in with tab indentation.

#!/bin/bash

for i in 1 2 3 4 5

do

        echo "Welcome number: $i"

done

Execute mybash1.sh

Exercise 3:  This exercise pertains to for loops for repetitive tasks. Example for loop script is as follows (type it in and mind the indentation):

#!/bin/bash

for ((i=0;i<12;i++))

do

        echo "Welcome number: $i"

done

Create a new file called mybash2.sh. Can you modify the above code to create folders: lab2 to lab12?

 

Exercise 4: This exercise pertains to conditional statements in bash scripts. The conditional expressions in bash may use a C-like syntax as follows:

if ((<some C-like conditional>))

then

<commands>

fi

Create a new file called mybash3.sh. Can you modify the above code to create folders: lab02, lab03,..,lab09,.. lab12?

Arrays in Bash:

Syntax:

declare -a arrayname=(element1 element2 element3)

Example:

declare -a Unix=('Debian' 'Red hat' 'Red hat' 'Suse' 'Fedora');

Length of an array is queried as: ${#ArrayName[@]}

An example of array element access at the ith position:

 ${ArrayName[i]}

Putting it all together:

I want to run the amplification program on Lenna_org_1024.pgm, gaussian width = 11, and for sigma values: 0.3, 0.4, …1.1 (totaling 9 executions). Automate these lines:

./amplify Lenna_org_1024.pgm 11 0.3 2

./amplify Lenna_org_1024.pgm 11 0.4 2

./amplify Lenna_org_1024.pgm 11 0.5 2

:

./amplify Lenna_org_1024.pgm 11 1.1 2

Exercise 5:

I want to run the amplification program on Lenna_org_1024.pgm for sigma values: 0.3, 0.4, …1.1 AND

gaussian widths: 5, 7, 11, 15, and 19. Automate this execution.

 

Script away Lab 7!!