How to send back the value sent to the fallback?

Question

Is there a way to get and keep the value sent to the fallback/receive functions? Let's say, I want to send back Ethers that sent to my contract. Okay, existence of fallback function is enough to deal with receiving ether but I want to keep value sent to me. How can I do it?

Answer 1

If you want to send the amount back to the original sender, you can do this:

fallback() external payable {
     address _to = msg.sender;
     (bool success, ) = _to.call{value: msg.value}("");
     require(success, "send failed")
}

If you want to send to a specific address, replace the _to. You might face some complexities due to gas if your contract balance is zero, then send will fail.

Answer 2

The msg.value contains the amount of ETH that was received, so you can send that amount back to msg.sender.