How to retrieve a FileSystem Wallet in a .ts file

Question

I am new to learning Solana development. Is there any way to retrieve the keypair from a Filesystem path? I am doing a tutorial and I want to use the same keypair to sign transactions, instead of creating each time a new one.

Answer 1

Here's a reference that you can adapt. It generates a .env file with a new keypair if one does not already exist, otherwise it creates the keypair from the file.

export async function initializeKeypair(
  connection: web3.Connection
): Promise<web3.Keypair> {
  if (!process.env.PRIVATE_KEY) {
    console.log("Creating .env file")
    const signer = web3.Keypair.generate()
    fs.writeFileSync(".env", `PRIVATE_KEY=[${signer.secretKey.toString()}]`)
    await airdropSolIfNeeded(signer, connection)

    return signer
  }

  const secret = JSON.parse(process.env.PRIVATE_KEY ?? "") as number[]
  const secretKey = Uint8Array.from(secret)
  const keypairFromSecretKey = web3.Keypair.fromSecretKey(secretKey)
  await airdropSolIfNeeded(keypairFromSecretKey, connection)
  return keypairFromSecretKey
}

airdropSolIfNeeded is just a helper function to airdrop devnet SOL

async function airdropSolIfNeeded(
  signer: web3.Keypair,
  connection: web3.Connection
) {
  const balance = await connection.getBalance(signer.publicKey)
  console.log("Current balance is", balance / web3.LAMPORTS_PER_SOL)

  if (balance < web3.LAMPORTS_PER_SOL) {
    console.log("Airdropping 1 SOL...")
    const airdropSignature = await connection.requestAirdrop(
      signer.publicKey,
      web3.LAMPORTS_PER_SOL
    )

    const latestBlockHash = await connection.getLatestBlockhash()

    await connection.confirmTransaction(
      {
        blockhash: latestBlockHash.blockhash,
        lastValidBlockHeight: latestBlockHash.lastValidBlockHeight,
        signature: airdropSignature,
      },
      "finalized"
    )

    const newBalance = await connection.getBalance(signer.publicKey)
    console.log("New balance is", newBalance / web3.LAMPORTS_PER_SOL)
  }
}

From this template: https://github.com/Unboxed-Software/solana-npx-client-template/tree/with-keypair-env