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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​