mithuns1986 / query-metadata

Code to query metadata

query-metadata

Code to query metadata of an instance within AWS and provides JSON formatted output. The script uses the curl command to retrieve the metadata and jq tool to format the output as JSON.

#!/bin/bash

# Retrieve the metadata
metadata=$(curl -s http://169.254.169.254/latest/dynamic/instance-identity/document)

# Check if a specific data key is provided as an argument
if [ $# -eq 1 ]; then
  # Retrieve the value of the specified key
  value=$(echo "$metadata" | jq -r ".$1")
  
  # Output the value as JSON
  echo "{\"$1\": \"$value\"}"
else
  # Output the entire metadata as JSON
  echo "$metadata" | jq .
fi

To use this script, save it to a file (e.g., metadata.sh), make it executable (chmod +x metadata.sh), and run it. Optionally, you can provide a specific data key as an argument to retrieve its value individually.

Example usage:

# Retrieve and output the entire metadata
./metadata.sh

# Retrieve and output a specific data key individually
./metadata.sh instanceType

Explanation:

1. The script starts by using the curl command to retrieve the metadata from the instance metadata service. The metadata endpoint http://169.254.169.254/latest/dynamic/instance-identity/document provides information about the instance, such as instance ID, instance type, region, etc.

2. If an argument is provided when running the script ($# -eq 1), it assumes that a specific data key is provided, and it retrieves the value of that key from the metadata using jq tool. The -r flag is used with jq to output the value without quotes.

3. If no argument is provided, the entire metadata is outputted as JSON using jq .. The . represents the entire JSON document.

The script allows for easy retrieval of the metadata of an AWS instance in a JSON format. It can be extended to handle additional functionality as per specific requirements. Remember to run this script on an EC2 instance within AWS to access the instance metadata.