import { ethers } from 'ethers';
import { JsonRpcProvider, Provider } from '@ethersproject/providers';
/**
 * Get environment variable value
 * @param key Environment variable name
 * @param defaultValue Default value (if environment variable doesn't exist)
 * @returns Environment variable value
 */
export declare function getEnv(key: string, defaultValue?: string): Promise<string>;
/**
 * Get private key from environment variable
 * @param keyName Private key environment variable name, default is 'PRIVATE_KEY'
 * @returns Private key string
 */
export declare function getPrivateKey(keyName?: string): Promise<string>;
/**
 * Create Signer from environment variable
 * @param provider Ethereum Provider
 * @param keyName Private key environment variable name
 * @returns Ethereum wallet instance
 */
export declare function createSignerFromEnv(provider: Provider, keyName?: string): Promise<ethers.Wallet>;
/**
 * Create Provider from environment variable or parameter
 * @param rpcUrl RPC URL (optional)
 * @returns JsonRpcProvider instance
 */
export declare function createProvider(rpcUrl?: string): Promise<JsonRpcProvider>;
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