Linked Questions

182 votes
2 answers
52k views

What is the difference between a transaction and a call?

What is the difference between a transaction and a call? In some interfaces, I can interact with contracts via calls or via transactions. What is the difference between the two, and can contracts also ...
  • 7,316
117 votes
2 answers
84k views

Which cryptographic hash function does Ethereum use?

Many sources refer to the use of the "SHA3" cryptographic hash function within Ethereum, but the Ethereum project began before the SHA3 standard was finalised, and there was some confusion/controversy ...
  • 21.3k
26 votes
2 answers
21k views

How do I know how much gas to use when calling a contract?

When I am calling (sending a transaction to) a contract how do I determine how much gas to use? Is there a way to calculate this upfront & what happens if I send too much / too few gas?
  • 8,421
15 votes
3 answers
44k views

How to calculate transaction fee?

For calculating the transaction fee using web3js I am using it's gas price: eth.getTransaction("txhash").gasPrice multiplied by how much gas was actually used: eth.getTransactionReceipt("txhash")....
  • 577
14 votes
3 answers
11k views

Is it possible to build a private (permissioned) blockchain with Ethereum?

Ethereum is a great blockchain, but for some services the transaction fee is prohibitively too expensive. Is there any project and/or guideline on making Ethereum so it works on permissioned ...
  • 3,137
14 votes
3 answers
826 views

Why does Ethereum have gas?

Why does Ethereum have gas? What other approaches could Ethereum have used to work around the Halting Problem?
  • 80.8k
8 votes
2 answers
3k views

Who gets the fee from contract call?

Basically you don't need to pay fee for contract call, but if a contract method does lots of work, you need to add gas in contract call to prevent DoS attack like this: contract.method.call({gas: ...
8 votes
1 answer
7k views

What is the cost of using a Chainlink Oracle?

I use the market.link to check available jobs and each job has its own price in terms of link. My question is how many times this fee will be paid? For example: Let's say the API GET request costs 0....
  • 1,225
8 votes
1 answer
1k views

Can a transaction get lost?

Given that I am connected to the network with at least one peer, can I be sure that a transaction I sent will be executed (either with fail or success)? Is there a possibility that it will never make ...
  • 2,530
5 votes
1 answer
1k views

what is difference between "gas" "gas price" and "fee"?

Can we say that gas is the unit of transaction fee ? And gas price is the same transaction fee ? If so, why we do not use ether and wei instead of gas ?
  • 2,578
5 votes
2 answers
535 views

Call Smart Contract every 5 Second

Is it possible the call a method of a smart contract every 5 seconds? Lets say i want to call a webservice or an other smart contract in order to get the actual value? That is not possible or? In ...
  • 521
5 votes
3 answers
1k views

Can a "forward" smart contract forward the received ether to another "forward" smart contract which forwards it to an address?

I am pretty new to solidity. I am trying to create a smart contract which deploys another smart contract and transfers ether to the newly created contract when a payment greater than 0.01 ether is ...
  • 75
5 votes
1 answer
1k views

What's the difference in the ways of calling a contract function?

After I get an instance of a contract, there are 3 ways to call the contract function below: 1.testInstance.testfunc({from:eth.accounts[0]}) 2.testInstance.testfunc.sendTransaction({from:eth.accounts[...
4 votes
2 answers
792 views

why are Transactions paid in Gas and not just Ether directly [duplicate]

All the explanations I heard for the Gas usage, could imho also be dealt with in Ether directly. What is it that Gas does that couldn't be done with Ether directly?
4 votes
1 answer
6k views

How to Set Gas Price in Private Blockchain?

I admit that I don't understand Gas at all. But I think it is basically the currency which dapps use to interact with each other and the blockchain. Yes? If you're creating a custom/private network,...
  • 1,984

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