lightning-fundpsbt -- Command to populate PSBT inputs from the wallet ================================================================ SYNOPSIS -------- **fundpsbt** *satoshi* *feerate* *startweight* \[*minconf*\] \[*reserve*\] DESCRIPTION ----------- `fundpsbt` is a low-level RPC command which creates a PSBT using unreserved inputs in the wallet, optionally reserving them as well. *satoshi* is the minimum satoshi value of the output(s) needed (or the string "all" meaning use all unreserved inputs). If a value, it can be a whole number, a whole number ending in *sat*, a whole number ending in *000msat*, or a number with 1 to 8 decimal places ending in *btc*. *feerate* can be one of the feerates listed in lightning-feerates(7), or one of the strings *urgent* (aim for next block), *normal* (next 4 blocks or so) or *slow* (next 100 blocks or so) to use lightningd’s internal estimates. It can also be a *feerate* is a number, with an optional suffix: *perkw* means the number is interpreted as satoshi-per-kilosipa (weight), and *perkb* means it is interpreted bitcoind-style as satoshi-per-kilobyte. Omitting the suffix is equivalent to *perkb*. *startweight* is the weight of the transaction before *fundpsbt* has added any inputs. *minconf* specifies the minimum number of confirmations that used outputs should have. Default is 1. *reserve* is a boolean: if true (the default), then *reserveinputs* is called (successfully, with *exclusive* true) on the returned PSBT. EXAMPLE USAGE ------------- Let's assume the caller is trying to produce a 100,000 satoshi output. First, the caller estimates the weight of the core (typically 42) and known outputs of the transaction (typically (9 + scriptlen) * 4). For a simple P2WPKH it's a 22 byte scriptpubkey, so that's 164 weight. It calls "*fundpsbt* 100000sat slow 206", which succeeds, and returns the *psbt* and *feerate_per_kw* it used, the *estimated_final_weight* and any *excess_msat*. If *excess_msat* is greater than the cost of adding a change output, the caller adds a change output randomly to position 0 or 1 in the PSBT. Say *feerate_per_kw* is 253, and the change output is a P2WPKH (weight 164), that would cost the cost is around 41 sats. With the dust limit disallowing payments below 546 satoshis, we would only create a change output if *excess_msat* was greater or equal to 41 + 546. RETURN VALUE ------------ On success, returns the *psbt* containing the inputs, *feerate_per_kw* showing the exact numeric feerate it used, *estimated_final_weight* for the estimated weight of the transaction once fully signed, and *excess_msat* containing the amount above *satoshi* which is available. This could be zero, or dust. If *satoshi* was "all", then *excess_msat* is the entire amount once fees are subtracted for the weights of the inputs and startweight. If *reserve* was true, then a *reservations* array is returned, exactly like *reserveinputs*. On error the returned object will contain `code` and `message` properties, with `code` being one of the following: - -32602: If the given parameters are wrong. - -1: Catchall nonspecific error. - 301: Insufficient UTXOs to meet *satoshi* value. AUTHOR ------ Rusty Russell <> is mainly responsible. SEE ALSO -------- lightning-reserveinputs(7), lightning-unreserveinputs(7). RESOURCES --------- Main web site: