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Create Simple Transactions

Creating a transaction requires various steps:

  • Get the protocol parameters
  • Calculate the fee
  • Define the time-to-live (TTL) for the transaction
  • Build the transaction
  • Sign the transaction
  • Submit the transaction

Get protocol parameters

Get the protocol parameters and save them to protocol.json with:

cardano-cli query protocol-parameters \
--mainnet \
--out-file protocol.json

Get the transaction hash and index of the UTXO to spend:

cardano-cli query utxo \
--address $(cat payment.addr) \
--mainnet

Draft the transaction

Create a draft for the transaction and save it in tx.draft

note

For --tx-in we use the following syntax: TxHash#TxIx where TxHash is the transaction hash and TxIx is the index; for --tx-out we use: TxOut+Lovelace where TxOut is the hex encoded address followed by the amount in Lovelace. For the transaction draft --tx-out, --invalid-hereafter and --fee can be set to zero.

cardano-cli transaction build-raw \
--tx-in 4e3a6e7fdcb0d0efa17bf79c13aed2b4cb9baf37fb1aa2e39553d5bd720c5c99#4 \
--tx-out $(cat payment2.addr)+0 \
--tx-out $(cat payment.addr)+0 \
--invalid-hereafter 0 \
--fee 0 \
--out-file tx.draft

Calculate the fee

A simple transaction needs one input, a valid UTXO from payment.addr, and two outputs:

  • Output1: The address that receives the transaction.
  • Output2: The address that receives the change of the transaction.

Note that to calculate the fee you need to include the draft transaction

cardano-cli transaction calculate-min-fee \
--tx-body-file tx.draft \
--tx-in-count 1 \
--tx-out-count 2 \
--witness-count 1 \
--byron-witness-count 0 \
--mainnet \
--protocol-params-file protocol.json

Calculate the change to send back to payment.addr

all amounts must be in Lovelace:

expr <UTXO BALANCE> - <AMOUNT TO SEND> - <TRANSACTION FEE>

For example, if we send 10 ada from a UTxO containing 20 ada, the change to send back to payment.addr after paying the fee is: 9.832035 ada

expr 20000000 - 10000000 - 167965
9832035

Determine the TTL (time to Live) for the transaction

To build the transaction we need to specify the TTL (Time to live), this is the slot height limit for our transaction to be included in a block, if it is not in a block by that slot the transaction will be cancelled. So TTL = slot + N slots. Where N is the amount of slots you want to add to give the transaction a window to be included in a block.

Query the tip of the blockchain:

cardano-cli query tip --mainnet

Look for the value of slotNo

    {
"blockNo": 16829,
"headerHash": "3e6f59b10d605e7f59ba8383cb0ddcd42480ddcc0a85d41bad1e4648eb5465ad",
"slotNo": 369200
}

Calculate your TTL, for example: 369200 + 200 slots = 369400

Build the transaction

We write the transaction in a file, we will name it tx.raw.

cardano-cli transaction build-raw \
--tx-in 4e3a6e7fdcb0d0efa17bf79c13aed2b4cb9baf37fb1aa2e39553d5bd720c5c99#4 \
--tx-out $(cat payment2.addr)+10000000 \
--tx-out $(cat payment.addr)+9832035 \
--invalid-hereafter 369400 \
--fee 167965 \
--out-file tx.raw

Sign the transaction

Sign the transaction with the signing key payment.skey and save the signed transaction in tx.signed

cardano-cli transaction sign \
--tx-body-file tx.raw \
--signing-key-file payment.skey \
--mainnet \
--out-file tx.signed

Submit the transaction

cardano-cli transaction submit \
--tx-file tx.signed \
--mainnet

Check the balances

We must give it some time to get incorporated into the blockchain, but eventually, we will see the effect:

cardano-cli query utxo \
--address $(cat payment.addr) \
--mainnet

> TxHash TxIx Amount
> ----------------------------------------------------------------------------------------
> b64ae44e1195b04663ab863b62337e626c65b0c9855a9fbb9ef4458f81a6f5ee 1 9832035 lovelace
cardano-cli query utxo \
--address $(cat payment2.addr) \
--mainnet

> TxHash TxIx Amount
> ----------------------------------------------------------------------------------------
> b64ae44e1195b04663ab863b62337e626c65b0c9855a9fbb9ef4458f81a6f5ee 0 10000000 lovelace
note

--mainnet identifies the Cardano mainnet, for testnets use --testnet-magic 1097911063 instead.

References