Downloading Files with Progress and Retries

#!/bin/bash

# --- Configuration ---
DOWNLOAD_URL="https://example.com/some_file.zip" # Replace with your URL
OUTPUT_FILE="downloaded_file.zip"             # Desired local filename
MAX_RETRIES=5                                 # Max attempts for download
RETRY_DELAY=5                                 # Delay in seconds between retries

# --- Functions ---
log_message() {
    local type=$1
    local message=$2
    echo "[$(date +'%Y-%m-%m %H:%M:%S')] [$type] $message"
}

download_file() {
    local url=$1
    local output=$2
    local attempt=1

    while [ $attempt -le $MAX_RETRIES ]; do
        log_message INFO "Attempt $attempt of $MAX_RETRIES: Downloading $url to $output..."
        
        # Use curl to download with progress, retries, and follow redirects
        # -L: Follow redirects
        # -f: Fail silently (no output on HTTP errors)
        # -s: Silent mode (no progress meter or error messages)
        # --retry <num>: Retry n times (curl's own retry, useful but we add our own loop for more control/logging)
        # --retry-delay <sec>: Wait time between retries
        # -o: Write output to file instead of stdout
        # --progress-bar or -#: Show progress bar

        if curl -L -f -# -o "$output" "$url"; then
            log_message INFO "Download successful: $output"
            return 0 # Success
        else
            local curl_exit_code=$?
            log_message WARNING "Download failed (curl exit code: $curl_exit_code) for $url. Retrying in $RETRY_DELAY seconds..."
            attempt=$((attempt + 1))
            sleep $RETRY_DELAY
        fi
    done

    log_message ERROR "Failed to download $url after $MAX_RETRIES attempts."
    return 1 # Failure
}

# --- Main Script ---
log_message INFO "Script started."

if download_file "$DOWNLOAD_URL" "$OUTPUT_FILE"; then
    log_message INFO "File processing can continue with $OUTPUT_FILE."
    # Example: unzip "$OUTPUT_FILE"
else
    log_message ERROR "Script terminated due to download failure."
    exit 1
fi

log_message INFO "Script finished."