Robust File Download with Progress and Retries

#!/bin/bash

URL="https://speed.hetzner.de/100MB.bin" # Example URL for a large file
OUTPUT_FILE="downloaded_file.bin"
MAX_RETRIES=5
RETRY_DELAY=10 # seconds

echo "Attempting to download $URL to $OUTPUT_FILE"

for (( i=1; i<=MAX_RETRIES; i++ )); do
    echo "Download attempt $i of $MAX_RETRIES..."
    
    # Use curl for downloading:
    # -L: Follow redirects
    # -f: Fail silently on HTTP errors (4xx/5xx)
    # -o: Output file
    # -# or --progress-bar: Show a progress bar
    # --retry: Handled manually for custom delay
    # --connect-timeout: Maximum time allowed for connection
    # --max-time: Maximum time allowed for the transfer
    if curl -L -f -o "$OUTPUT_FILE" --progress-bar --connect-timeout 10 --max-time 30 "$URL"; then
        echo "Download successful!"
        break
    else
        ERROR_CODE=$?
        echo "Download failed with curl exit code: $ERROR_CODE"
        if [ $i -lt $MAX_RETRIES ]; then
            echo "Retrying in $RETRY_DELAY seconds..."
            sleep "$RETRY_DELAY"
        else
            echo "Maximum retries reached. Download failed after $MAX_RETRIES attempts."
            exit 1
        fi
    fi
done

if [ -f "$OUTPUT_FILE" ]; then
    echo "Downloaded file size: $(du -h "$OUTPUT_FILE" | awk '{print $1}')"
    # Optional: Verify checksum here (refer to previous snippet)
    rm "$OUTPUT_FILE"
    echo "Cleaned up $OUTPUT_FILE"
fi