Creating Bash Scripts Choices And Loops – Part 4

You’ve encountered user interaction with your scripts, asking what the user’s name is and so on. You’ve also looked at creating loops within the script to either count or simply do something several times. Let’s combine and expand some more.

Let’s bring in another command, CHOICE, along with some nested IF and ELSE statements. Start by creating a new script called mychoice.sh.

Step 1

The mychoice.sh script is beginning to look a lot more complex. What we have here is a list of four choices, with three possible options. The options: Mint, Is, and Awesome will be displayed if the user presses the correct option key. If not, then the menu will reappear, the fourth choice.

Step 2

If you follow the script through you soon get the hang of what’s going on, based on what we’ve already covered. WHILE, IF, and ELSE, with the FI closing loop statement will run through the options and bring you back to the start if you pick the wrong option.

Step 3

You can, of course, increase the number of choices but you need to make sure that you match the number of choices to the number of IF statements. The script can quickly become a very busy screen to look at. This lengthy script is another way of displaying a menu, this time with a fancy colour scheme too.

Step 4

You can use the arrow keys and Enter in the menu setup in the script. Each choice is an external command that feeds back various information. Play around with the commands and choices, and see what you can come up with. It’s a bit beyond what we’ve looked at but it gives a good idea of what can be achieved.

Creating A Backup Task Script

One of the most well used examples of Bash scripting is the creation of a backup routine, one that automates the task as well as adding some customisations along the way.

Step 1

A very basic backup script would look something along the lines of: #!/bin/bash, then,

tar cvfz ~/backups/my-backup.tgz ~/Documents/. This will create a compressed file backup of the ~/Documents folder, with everything in it, and put it in a folder called /backups with the name my-backup.tgz.

Step 2

While perfectly fine, we can make the simple script a lot more interactive. Let’s begin with defining

some variables. Enter the text in the screenshot into a new backup. sh script. Notice that we’ve misspelt ‘source’ as ‘sauce’, this is because there’s already a built-in command called ‘source’ hence the different spelling on our part.

Step 3

The previous script entries allowed you to create a Time Stamp, so you know when the backup was

taken. You also created a ‘dest’ variable, which is the folder where the backup file will be created (~/backups). You can now add a section of code to first check if the ~/backups folder exits, if not, then it creates one.

Step 4

Once the ~/backups folder is created, we can now create a new subfolder within it based on the

Time Stamp variables you set up at the beginning. Add mkdir -p $dest/”$day $month $year”. It’s in here that you put the backup file relevant to that day/month/year.

Step 5

With everything in place, you can now enter the actual backup routine, based on the Tar command from Step 5. Combined with the variables, you have: tar cvfz $dest/”$day $month $year”/DocumentsBackup.tgz $sauce. In the screenshot, we added a handy “Now backing up...” echo command.

Step 6

Finally, you can add a friendly message: echo “Backup complete. All done...”. The completed script isn’t too over-complex and it can be easily customised to include any folder within your Home area, as well as the entire Home area itself.

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