Bitcoin Forum

I notice that is a main() function in bitcoin-tx.cpp. This main() is not the main function of bitcoin core. Because the main function is in bitcoind.cpp

So why there is a main() in bitcoin-tx.cpp ?

There is a separate binary called bitcoin-tx which lets you do some transaction specific things without needing to run the full Bitcoin Core. It needs a main function for that binary to work.

Likewise, there are main functions in bitcoin-cli.cpp and qt/bitcoin.cpp as those are for separate binaries that need main functions too (bitcoin-cli and bitcoin-qt respectively).

thank you. should have seen that

It looks like bitcoin-tx.cpp is never built into the bincoind binary of Bitcoin core, isn't  it?

No, it is not. bitcoin-tx.cpp is for bitcoin-tx, a completely separate binary. It only exists to provide the separate bitcoin-tx binary.

Thank you. Now I use the bitcoin-tx binary.

bitcoin-tx -create in=0fb9df5614be8b33be0434ce4062750d83f1b7ce05cc1296604f82eb9abf802b:0 outscript=0.00159999:"DUP HASH160 0x14 0x6793a38f79b8cd51dbb6face6dc75a4af5c1bf29 EQUALVERIFY CHECKSIG"

and got the return value
02000000012b80bf9aeb824f609612cc05ceb7f1830d756240ce3404be338bbe1456dfb90f00000 00000ffffffff01ff700200000000001976a9146793a38f
79b8cd51dbb6face6dc75a4af5c1bf2988ac00000000

i understand the outscript format. 0.00159999 is the value to be spent. What about the in format ? what is 0fb9df56..... ? It is previous tx or scriptSig?

Read https://bitcoin.org/en/developer-reference#raw-transaction-format

I read the link about raw transaction format. It says raw transaction has version, tx_in count, Tx_in, TX_out count, Tx_out and lock time.

I can't relate this format to the hex value in the input part.

TxIn (transaction input) structure consists of prevOut, scriptSig and sequence.
In bitcoind code prevOut has type COutPoint which consists of txid and output number.
So the "in=" you quoted means the transaction will spend the output with index 0 from transaction with id 0fb9df5614be8b33be0434ce4062750d83f1b7ce05cc1296604f82eb9abf802b, if the signature in scriptSig will be correct for
the corresponding TxOut's pk_script.

I guess the signature is generated from a key in your wallet file, if it can sign this input.

So in "bitcoin-tx -create in=0fb9df5614be8b33be0434ce4062750d83f1b7ce05cc1296604f82eb9abf802b:0 ...."
The 0fb9df5614be8b33be0434ce4062750d83f1b7ce05cc1296604f82eb9abf802b is the txid.

Thank you.

We can use the command "bitcoin-tx -create --help"  to see the explanation of the options in the command.