CLI scripting basics in AWS - Step-by-Step Execution

Process Flow - CLI scripting basics

Start Script

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Write CLI Command

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Run Command in Terminal

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Command Executes

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Output Received

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Use Output or Next Command

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Repeat or End Script

This flow shows how a CLI script runs commands one by one, gets output, and uses it for next steps or finishes.

Execution Sample

AWS

aws s3 ls
aws s3 mb s3://my-bucket-example
aws s3 cp file.txt s3://my-bucket-example/

This script lists S3 buckets, creates a new bucket, then uploads a file to it.

Process Table

Step	Command	Action	Output	Next Step
1	aws s3 ls	List all S3 buckets	Shows existing buckets	Proceed to create bucket
2	aws s3 mb s3://my-bucket-example	Make new bucket	Bucket created confirmation	Proceed to upload file
3	aws s3 cp file.txt s3://my-bucket-example/	Copy file to bucket	File upload success message	End script

💡 All commands executed successfully, script ends.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
bucket_name	undefined	undefined	my-bucket-example	my-bucket-example
file_uploaded	false	false	false	true

Key Moments - 2 Insights

Why do we run commands one after another instead of all at once?

Commands run step-by-step to ensure each finishes successfully before the next starts, as shown in execution_table rows 1 to 3.

What happens if the bucket already exists when we try to create it?

The create bucket command will fail or show an error, stopping the script or requiring error handling, which is not shown in this simple flow.

Visual Quiz - 3 Questions

Look at the execution table, what is the output after step 1?

A Bucket created confirmation

B Shows existing buckets

C File upload success message

D Error message

💡 Hint

Check the Output column in row 1 of the execution_table.

At which step does the file get uploaded to the bucket?

A Step 1

B Step 2

C Step 3

D No file upload in script

💡 Hint

Look at the Command and Action columns in the execution_table.

If the bucket name changes, which variable in variable_tracker updates?

A bucket_name

B file_uploaded

C Start

D Output

💡 Hint

Refer to the variable_tracker rows and see which variable holds the bucket name.

Concept Snapshot

CLI scripting basics:
- Write commands line by line
- Run commands in order
- Each command outputs result
- Use output for next commands
- Scripts automate cloud tasks

Full Transcript

This lesson shows how CLI scripts run commands one after another. First, a command is written and run in the terminal. The command executes and returns output. The script uses this output or moves to the next command. For example, listing S3 buckets, creating a bucket, then uploading a file. Variables like bucket name and file upload status change as commands run. Running commands step-by-step ensures success before continuing. If errors occur, scripts may stop or need handling. This basic flow helps automate cloud tasks using CLI.