Using Ubuntu OS, write and implement ONE (1) bash shell script (only one script should be written for the whole Question 3): Operating Systems Assignment, SUSS, Singapore, Singapore

Question 3

Implement system security and access control in the Linux operating system.

Using Ubuntu OS, write and implement ONE (1) bash shell script (only one script should be written for the whole Question 3). Use the root account to execute the script. The script will be executed with no arguments, and it can be executed in any folder.

The bash shell script should have the following specifications:

Part (a)

1. The script will list the filenames of all image files (excluding hidden image files and image files in sub-folders) in the current folder with the extension of .png and jpg on screen, Note that only the filenames and size (in bytes) should be displayed.

2. It will display the total size (in bytes) of all the ._png and .jpg image files in the current folder.

3. It will then display the following message depending on the total size of all the .png and jpg image files in the current folder.

•  Less than 5000000 bytes, display “total image size is small”
•  More than or equal to 5000000 bytes, display “total image size is NOT small”
  (15 marks)

Part (b)

4. The script will then display the permissions of the .png and .jpg image files in the following format.

[Filename] owner [owner-permission] group [group-permission] others [others-permission]
Example of display:

image 1.jpg owner rwx group rw- others r-x

image2.jpg owner r– group -wx others -w-

image3.png owner rwx group rwx others rwx

5. It will prompt the user to enter a keyword of owner, group or others. It will keep prompting the user to enter the keyword until the user enter a valid keyword.

6. It will follow by prompting the user to enter another keyword of read, write or execute. It will keep asking the user to enter the keyword until the user enter a valid keyword.

Part (c)

7. The script will then invert the permission of the image files according to the
following:

If the user has entered owner and write, then the owner write permissions of the .png and .jpg image files will invert. That means if there is an owner write permission on the file, then it will invert to no write permission, and vice versa. (e.g. If imagel jpg