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LIGHTNING-FUNDPSBT(7) LIGHTNING-FUNDPSBT(7) NAME lightning-fundpsbt -- Command to populate PSBT inputs from the wallet SYNOPSIS fundpsbt satoshi feerate startweight [minconf] [reserve] [locktime] [min_witness_weight] [excess_as_change] [nonwrapped] [opening_an- chor_channel] DESCRIPTION fundpsbt is a low-level RPC command which creates a PSBT using unre- served inputs in the wallet, optionally reserving them as well. • satoshi (sat_or_all): 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 (feerate): Used for the transaction as initial feerate. The default is normal. • startweight (u32): The weight of the transaction before fundpsbt has added any inputs. • minconf (u32, optional): The minimum number of confirmations that used outputs should have. The default is 1. • reserve (u32, optional): If not zero, then reserveinputs is called (successfully, with exclusive true) on the returned PSBT for this number of blocks. The default is 72 blocks. • locktime (u32, optional): The locktime of the transaction. if not set, it is set to a recent block height. • min_witness_weight (u32, optional): Minimum weight to use for a UTXO's witness. If the actual witness weight is greater than the provided minimum, the actual witness weight will be used. • excess_as_change (boolean, optional): Flag to add a change output for the excess sats. • nonwrapped (boolean, optional): To signal to filter out any p2sh- wrapped inputs from funding this PSBT. (added v23.02) • opening_anchor_channel (boolean, optional): To signel that it needs emergency reserve for anchors so that we can lowball our commitment tx fees, and min-emergency-msat for reserving some sats for closing anchor channels. (added v23.08) RETURN VALUE On success, an object is returned, containing: • psbt (string): Unsigned PSBT which fulfills the parameters given. • feerate_per_kw (u32): The feerate used to create the PSBT, in satoshis-per-kiloweight. • estimated_final_weight (u32): The estimated weight of the transac- tion once fully signed. • excess_msat (msat): The amount above satoshi which is available. This could be zero, or dust; it will be zero if change_outnum is also returned. • change_outnum (u32, optional): The 0-based output number where change was placed (only if parameter excess_as_change was true and there was sufficient funds). • reservations (array of objects, optional): If reserve was true or a non-zero number, just as per lightning- reserveinputs(7).: • txid (txid): The txid of the transaction. • vout (u32): The 0-based output number. • was_reserved (boolean) (always false): Whether this output was previously reserved. • reserved (boolean) (always true): Whether this output is now re- served. • reserved_to_block (u32): The blockheight the reservation will ex- pire. If excess_as_change is true and the excess is enough to cover an addi- tional output above the dust_limit, then an output is added to the PSBT for the excess amount. The excess_msat will be zero. A change_outnum will be returned with the index of the change output. ERRORS 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 <<rusty@rustcorp.com.au>> is mainly responsible. SEE ALSO lightning-utxopsbt(7), lightning-reserveinputs(7), lightning-unre- serveinputs(7) RESOURCES Main web site: <https://github.com/ElementsProject/lightning> 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 124 weight. It calls "fundpsbt 100000sat slow 166", which succeeds, and returns the psbt and feerate_per_kw it used, the estimated_final_weight and any ex- cess_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 124), the cost is around 31 sats. With the dust limit disallowing pay- ments below 546 satoshis, we would only create a change output if ex- cess_msat was greater or equal to 31 + 546. EXAMPLES Example 1: Request: $ lightning-cli fundpsbt -k "satoshi"=1000000 "feerate"="253perkw" "startweight"=250 "reserve"=0 { "id": "example:fundpsbt#1", "method": "fundpsbt", "params": { "satoshi": 1000000, "feerate": "253perkw", "startweight": 250, "reserve": 0 } } Response: { "psbt": "cHNidP8BAgQCAAAAAQMEbwAAAAEEAQpsbt310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000310000", "feerate_per_kw": 253, "estimated_final_weight": 693, "excess_msat": 196962507000, "change_outnum": 0 } Example 2: Request: $ lightning-cli fundpsbt -k "satoshi"=500000 "feerate"="urgent" "startweight"=166 "reserve"=0 "excess_as_change"=True "min_witness_weight"=110 { "id": "example:fundpsbt#2", "method": "fundpsbt", "params": { "satoshi": 500000, "feerate": "urgent", "startweight": 166, "reserve": 0, "excess_as_change": true, "min_witness_weight": 110 } } Response: { "psbt": "cHNidP8BAgQCAAAAAQMEbwAAAAEEAQpsbt410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000410000", "feerate_per_kw": 11000, "estimated_final_weight": 612, "excess_msat": 0, "change_outnum": 0 } Core Lightning v25.02 LIGHTNING-FUNDPSBT(7)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | AUTHOR | SEE ALSO | RESOURCES | USAGE | EXAMPLES
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