Downloading Files Conditionally with curl (If-Modified-Since)

#!/bin/bash

DOWNLOAD_URL="https://raw.githubusercontent.com/username/repo/main/some_file.txt" # Replace with a real URL
LOCAL_PATH="./downloaded_file.txt"

# Ensure the URL is accessible for testing purposes. For example:
# DOWNLOAD_URL="https://example.com/some_asset.zip"
# If you don't have a specific file, you can use a generic test file:
# DOWNLOAD_URL="https://www.google.com/robots.txt"

# Check if the file exists locally
if [[ -f "$LOCAL_PATH" ]]; then
  echo "Local file '$LOCAL_PATH' exists. Checking for newer version..."
  # Download only if newer than local file
  curl -s -L -R -z "$LOCAL_PATH" -o "$LOCAL_PATH" "$DOWNLOAD_URL"
  if [[ $? -eq 0 ]]; then
    echo "File downloaded/updated (if newer)."
  else
    echo "No update needed or download failed."
  fi
else
  echo "Local file '$LOCAL_PATH' does not exist. Downloading..."
  # Download the file directly
  curl -s -L -R -o "$LOCAL_PATH" "$DOWNLOAD_URL"
  if [[ $? -eq 0 ]]; then
    echo "File downloaded successfully."
  else
    echo "Error: Failed to download file."
    exit 1
  fi
fi

echo "
Contents of $LOCAL_PATH:"
cat "$LOCAL_PATH"

# Clean up example file
rm -f "$LOCAL_PATH"