Instructions for the Command-Line Interface
### The Basics
Monero works a little differently to what you may have become accustomed to from other @cryptocurrencies. In the case of a digital currency like Bitcoin and its many derivatives merchant payment systems will usually create a new recipient @address for each payment or user.
However, because Monero has @stealth-addresses there is no need to have separate recipient addresses for each payment or user, and a single @account address can be published. Instead, when receiving payments a merchant will provide the person paying with a "payment ID".
A @payment-ID is a hexadecimal string that is 64 characters long, and is normally randomly created by the merchant. An example of a payment ID is:
```
666c75666679706f6e7920697320746865206265737420706f6e792065766572
```
### Checking for a Payment in monero-wallet-cli
If you want to check for a payment using monero-wallet-cli you can use the "payments" command followed by the payment ID or payment IDs you want to check. For example:
```
[wallet 49VNLa]: payments 666c75666679706f6e7920697320746865206265737420706f6e792065766572
payment transaction height amount unlock time
666c75666679706f6e79206973207 7ba4cd810c9b4096869849458181e98e 441942 30.00000 0
[wallet 49VNLa]: █
```
If you need to check for payments programmatically, then details follow the next section.
### Receiving a Payment Step-by-Step
* Generate a random 64 character hexadecimal string for the payment
* Communicate the payment ID and Monero address to the individual who is making payment
* Check for the payment using the "payments" command in monero-wallet-cli
### Checking for a Payment Programmatically
In order to check for a payment programmatically you can use the get_payments or get_bulk_payments JSON RPC API calls.
*get_payments*: this requires a payment_id parameter with a single payment ID.
*get_bulk_payments*: this is the preferred method, and requires two parameters, payment_ids - a JSON array of payment IDs - and an optional min_block_height - the block height to scan from.
An example of returned data is as follows:
```
[ monero->~ ]$ curl -X POST http://127.0.0.1:18500/json_rpc -d '{"jsonrpc":"2.0","method":"get_bulk_payments","id":"test", "params":{"payment_ids": ["666c75666679706f6e7920697320746865206265737420706f6e792065766572"]}}' -H "Content-Type: application/json"
{
"id": "test",
"jsonrpc": "2.0",
"result": {
"payments": [{
"amount": 30000000000000,
"block_height": 441942,
"payment_id": "666c75666679706f6e7920697320746865206265737420706f6e792065766572",
"tx_hash": "7ba4cd810c9b4096869849458181e98e18b6474ab66415de0f4ccf7ab1162fdf",
"unlock_time": 0
}]
}
}
```
It is important to note that the amounts returned are in base Monero units and not in the display units normally used in end-user applications. Also, since a transaction will typically have multiple outputs that add up to the total required for the payment, the amounts should be grouped by the tx_hash or the payment_id and added together. Additionally, as multiple outputs can have the same amount, it is imperative not to try and filter out the returned data from a single get_bulk_payments call.
Before scanning for payments it is useful to check against the daemon RPC API (the get_info RPC call) to see if additional blocks have been received. Typically you would want to then scan only from that received block on by specifying it as the min_block_height to get_bulk_payments.
### Programatically Scanning for Payments
* Get the current block height from the daemon, only proceed if it has increased since our last scan
* Call the get_bulk_payments RPC API call with our last scanned height and the list of all payment IDs in our system
* Store the current block height as our last scanned height
* Remove duplicates based on transaction hashes we have already received and processed