119 lines
4.9 KiB
Markdown
119 lines
4.9 KiB
Markdown
lightning-fundpsbt -- Command to populate PSBT inputs from the wallet
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================================================================
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SYNOPSIS
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--------
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**fundpsbt** *satoshi* *feerate* *startweight* \[*minconf*\] \[*reserve*\] \[*locktime*\] \[*min_witness_weight*\] \[*excess_as_change*\]
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DESCRIPTION
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-----------
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`fundpsbt` is a low-level RPC command which creates a PSBT using unreserved
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inputs in the wallet, optionally reserving them as well.
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*satoshi* is the minimum satoshi value of the output(s) needed (or the
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string "all" meaning use all unreserved inputs). If a value, it can
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be a whole number, a whole number ending in *sat*, a whole number
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ending in *000msat*, or a number with 1 to 8 decimal places ending in
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*btc*.
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*feerate* can be one of the feerates listed in lightning-feerates(7),
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or one of the strings *urgent* (aim for next block), *normal* (next 4
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blocks or so) or *slow* (next 100 blocks or so) to use lightningd's
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internal estimates. It can also be a *feerate* is a number, with an
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optional suffix: *perkw* means the number is interpreted as
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satoshi-per-kilosipa (weight), and *perkb* means it is interpreted
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bitcoind-style as satoshi-per-kilobyte. Omitting the suffix is
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equivalent to *perkb*.
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*startweight* is the weight of the transaction before *fundpsbt* has
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added any inputs.
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*minconf* specifies the minimum number of confirmations that used
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outputs should have. Default is 1.
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*reserve* is either boolean or a number: if *true* or a non-zero
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number then *reserveinputs* is called (successfully, with
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*exclusive* true) on the returned PSBT for this number of blocks (or
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72 blocks if *reserve* is simply *true*).
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*locktime* is an optional locktime: if not set, it is set to a recent
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block height.
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*min_witness_weight* is an optional minimum weight to use for a UTXO's
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witness. If the actual witness weight is greater than the provided minimum,
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the actual witness weight will be used.
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*excess_as_change* is an optional boolean to flag to add a change output
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for the excess sats.
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EXAMPLE USAGE
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-------------
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Let's assume the caller is trying to produce a 100,000 satoshi output.
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First, the caller estimates the weight of the core (typically 42) and
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known outputs of the transaction (typically (9 + scriptlen) * 4). For
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a simple P2WPKH it's a 22 byte scriptpubkey, so that's 124 weight.
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It calls "*fundpsbt* 100000sat slow 166", which succeeds, and returns
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the *psbt* and *feerate_per_kw* it used, the *estimated_final_weight*
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and any *excess_msat*.
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If *excess_msat* is greater than the cost of adding a change output,
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the caller adds a change output randomly to position 0 or 1 in the
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PSBT. Say *feerate_per_kw* is 253, and the change output is a P2WPKH
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(weight 124), the cost is around 31 sats. With the dust limit disallowing
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payments below 546 satoshis, we would only create a change output
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if *excess_msat* was greater or equal to 31 + 546.
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RETURN VALUE
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------------
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[comment]: # (GENERATE-FROM-SCHEMA-START)
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On success, an object is returned, containing:
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- **psbt** (string): Unsigned PSBT which fulfills the parameters given
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- **feerate_per_kw** (u32): The feerate used to create the PSBT, in satoshis-per-kiloweight
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- **estimated_final_weight** (u32): The estimated weight of the transaction once fully signed
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- **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
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- **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)
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- **reservations** (array of objects, optional): If *reserve* was true or a non-zero number, just as per lightning-reserveinputs(7):
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- **txid** (txid): The txid of the transaction
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- **vout** (u32): The 0-based output number
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- **was_reserved** (boolean): Whether this output was previously reserved (always *false*)
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- **reserved** (boolean): Whether this output is now reserved (always *true*)
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- **reserved_to_block** (u32): The blockheight the reservation will expire
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[comment]: # (GENERATE-FROM-SCHEMA-END)
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If *excess_as_change* is true and the excess is enough to cover
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an additional output above the `dust_limit`, then an output is
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added to the PSBT for the excess amount. The *excess_msat* will
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be zero. A *change_outnum* will be returned with the index of
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the change output.
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On error the returned object will contain `code` and `message` properties,
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with `code` being one of the following:
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- -32602: If the given parameters are wrong.
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- -1: Catchall nonspecific error.
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- 301: Insufficient UTXOs to meet *satoshi* value.
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AUTHOR
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------
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Rusty Russell <<rusty@rustcorp.com.au>> is mainly responsible.
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SEE ALSO
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--------
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lightning-utxopsbt(7), lightning-reserveinputs(7), lightning-unreserveinputs(7).
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RESOURCES
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---------
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Main web site: <https://github.com/ElementsProject/lightning>
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[comment]: # ( SHA256STAMP:635cc321d158bcdb3ca24f13c9955cc9b867e34247c1cf3d91edbbe21eb06a48)
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