Parsing INI-like Configuration Files in Bash

#!/bin/bash

# Define the configuration file
CONFIG_FILE="config.ini"

# Create a dummy config.ini for demonstration if it doesn't exist
if [ ! -f "$CONFIG_FILE" ]; then
  echo "; This is a comment
[database]
host=localhost
port=3306
user=dbuser
password=dbpass

[application]
name=MyApp
environment=production
loglevel=info" > "$CONFIG_FILE"
  echo "Created a sample $CONFIG_FILE."
fi

# Function to parse INI file
parse_ini_file() {
  local ini_file="$1"
  local section=default
  
  while IFS='=' read -r key value || [[ -n "$key" ]]; do
    # Remove leading/trailing whitespace
    key=$(echo "$key" | xargs)
    value=$(echo "$value" | xargs)

    # Skip comments and empty lines
    [[ "$key" =~ ^\s*# ]] && continue
    [[ "$key" =~ ^\s*; ]] && continue
    [[ -z "$key" ]] && continue

    # Handle sections: [section_name]
    if [[ "$key" =~ ^\[(.*)\]$ ]]; then
      section="${BASH_REMATCH[1]}"
      continue
    fi

    # Export key-value pairs as variables prefixed with section_ (uppercase)
    VAR_NAME="$(echo "${section^^}_${key^^}" | sed 's/[^A-Z0-9_]/_/g')"
    export "$VAR_NAME"="$value"
    echo "Loaded: $VAR_NAME = $value"

  done < "$ini_file"
}

# Call the parser function
parse_ini_file "$CONFIG_FILE"

echo "
--- Loaded Configuration ---"
# Example of accessing loaded variables
echo "DB Host: $DATABASE_HOST"
echo "App Name: $APPLICATION_NAME"
echo "Environment: $APPLICATION_ENVIRONMENT"

# Accessing a variable that might not exist for demonstration
echo "Non-existent variable: $DATABASE_NONEXISTENT_KEY (empty if not found)"

echo "Script finished."