README.md

🛠️ Working with Functions in Shell Scripting

In this mini-project, you'll write a Bash script that automates the setup of EC2 instances and S3 buckets. The focus is on using functions to organize the logic, improve readability, and support reuse.

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🎯 Project Objectives

• Check if a script has the required argument.
• Validate the argument against expected environment values.
• Verify that AWS CLI is installed.
• Confirm that the AWS_PROFILE environment variable is set.
• Use Bash functions to structure logic clearly.
• Understand how to configure AWS profiles for multiple environments.

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📂 File Setup

1. Create the Script File

vim aws_setup.sh

2. Make it Executable

chmod +x aws_setup.sh

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⚙️ Refactored Script Using Functions

#!/bin/bash

# ENVIRONMENT passed as an argument
ENVIRONMENT=$1

# Function to check if argument is passed
check_num_of_args() {
  if [ "$#" -ne 1 ]; then
    echo "Usage: $0 <environment>"
    exit 1
  fi
}

# Function to activate environment-specific logic
activate_infra_environment() {
  if [ "$ENVIRONMENT" == "local" ]; then
    echo "Running script for Local Environment..."
  elif [ "$ENVIRONMENT" == "testing" ]; then
    echo "Running script for Testing Environment..."
  elif [ "$ENVIRONMENT" == "production" ]; then
    echo "Running script for Production Environment..."
  else
    echo "Invalid environment specified. Please use 'local', 'testing', or 'production'."
    exit 2
  fi
}

# Function to check if AWS CLI is installed
check_aws_cli() {
  if ! command -v aws &> /dev/null; then
    echo "AWS CLI is not installed. Please install it before proceeding."
    return 1
  fi
}

# Function to check if AWS_PROFILE is set
check_aws_profile() {
  if [ -z "$AWS_PROFILE" ]; then
    echo "AWS profile environment variable is not set."
    return 1
  fi
}

# Function calls
check_num_of_args "$@"
activate_infra_environment
check_aws_cli
check_aws_profile

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🔍 Code Explanation

• Function Names are descriptive and clarify script structure.
• Function Calls are placed at the end, mimicking professional shell scripting style.
• "$@" ensures proper argument passing to functions.

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✅ Sample Output (Plaintext)

$ ./aws_setup.sh testing
Running script for Testing Environment...

$ ./aws_setup.sh
Usage: ./aws_setup.sh <environment>

$ ./aws_setup.sh staging
Invalid environment specified. Please use 'local', 'testing', or 'production'.

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🧾 How to Create AWS Profiles for Testing & Production

Use the aws configure --profile <name> command to set up named AWS profiles:

aws configure --profile testing
aws configure --profile production

This command prompts you for:

• AWS Access Key ID
• AWS Secret Access Key
• Default Region Name
• Default Output Format

These settings will be saved in two files:

~/.aws/credentials

[default]
aws_access_key_id = YOUR_ACCESS_KEY_ID
aws_secret_access_key = YOUR_SECRET_KEY

[testing]
aws_access_key_id = YOUR_TESTING_KEY_ID
aws_secret_access_key = YOUR_TESTING_SECRET_KEY

[production]
aws_access_key_id = YOUR_PRODUCTION_KEY_ID
aws_secret_access_key = YOUR_PRODUCTION_SECRET_KEY

~/.aws/config

[default]
region = us-east-1
output = json

[profile testing]
region = us-west-1
output = json

[profile production]
region = us-west-2
output = json

Activate a specific profile for the current terminal session:

export AWS_PROFILE=testing

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❗ Troubleshooting Tips

Issue	Cause	Fix
Usage: ./aws_setup.sh <environment>	Missing required argument	Pass environment like local, testing, etc.
AWS CLI is not installed	CLI not found in PATH	Run: sudo apt install awscli
AWS profile environment variable is not set	Missing AWS_PROFILE	Run: export AWS_PROFILE=testing
Unrecognized environment value	Invalid input like dev or qa	Use only: local, testing, or production

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🧠 Additional Notes

• command -v aws: Tests if AWS CLI exists.
• -z "$VAR": Tests if variable is empty.
• Use return 1 in functions to gracefully exit without crashing the entire script.

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🏁 Summary

✅ What You Learned:

• How to use functions to structure and organize Bash scripts.
• Input validation and command-line argument checking.
• AWS CLI detection and environment profile validation.
• How to configure multiple AWS profiles for different environments.
• Creating cleaner, modular, and reusable scripts.

This approach mirrors what professionals do in real-world DevOps automation workflows. Great work!

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