DEV Community: rahuldev-17

Miscellaneous Tips

rahuldev-17 — Fri, 03 Nov 2023 12:00:03 +0000

How to get vim to use another vimrc file

Vim will use the ~/.vimrc by default. If you wish to specify another initialization script, just do:

vim -u <PATH TO FILE>

Where is my .vimrc file?

:echo $VIM
:echo $MYVIMRC

OSError - Errno 13 Permission denied

run id in the terminal to get your user_id and group_id

Go the directory/partition where you are facing the challenge. Open terminal, type id then press enter. This will show you your user_id and group_id

then type
chown -R user-id:group-id .

Replace user-id and group-id

. at the end indicates current partition / repository

chown -R 1001:1001 .
(that was my case)

How do I run .sh scripts?

Give execute permission to your script:

chmod +x /path/to/yourscript.sh

And to run your script:

/path/to/yourscript.sh
Since . refers to the current directory: if yourscript.sh is in the current directory, you can simplify this to:

./yourscript.sh

check file size

ls -sh

stat file

nix VPS running out of memory?

rahuldev-17 — Sun, 23 Jul 2023 05:22:14 +0000

Note to me: If your VPS is running out memory while installing another application, then quick fix:

check disk usage:

$df -h

find files greater than 500MB

sudo find / -type f -size +500M -exec ls -lh {} \;

If you understand and are sure of what files are not being used by you, database or system, remove them.

Where is RouteServiceProvider code in Laravel codes?

rahuldev-17 — Sat, 22 Jul 2023 09:49:12 +0000

So.. while reading Laravel documentation, did you wonder the same? if yes, here you go:
The RouteServiceProvider code in Laravel is located in the app/Providers/RouteServiceProvider.php file. This file is responsible for registering the application's routes and middleware. It also defines the default namespace for controller routes.

How to find the RouteServiceProvider code

To find the RouteServiceProvider code in your Laravel project,navigate to app/Providers/ and open RouteServiceProvider.php file.

but you need more help so...

The RouteServiceProvider code

The RouteServiceProvider code is divided into two main sections:

The boot() method: This method registers the application's routes and middleware.
The map() method: This method defines the default namespace for controller routes.

The `boot()` method

The boot() method uses the Route facade to register the application's routes. The Route facade provides a number of methods for registering routes, including:

get(): Registers a GET route.
post(): Registers a POST route.
put(): Registers a PUT route.
delete(): Registers a DELETE route.

The `map()` method

The map() method defines the default namespace for controller routes. The default namespace is the namespace that is used to prefix controller route declarations. For example, if the default namespace is App\Http\Controllers, then the following route declaration would route requests to the HomeController class:

Route::get('/', 'HomeController@index');

The `RouteServiceProvider` code is a critical part of the Laravel framework.

It is responsible for registering the application's routes and middleware, and it also defines the default namespace for controller routes.

How to go deep in ethers one function at a time: ParseUnits()

rahuldev-17 — Mon, 10 Jan 2022 18:57:58 +0000

Time to get familiar with your tool-set. Okay, so how does Ricmoo write his js/ts functions? Let us see ParseUnits().

It is written in Typescript at ethers.js/packages/units/src.ts/index.ts. Here it goes:

export function parseUnits(value: string, unitName?: BigNumberish): BigNumber {
    if (typeof(value) !== "string") {
        logger.throwArgumentError("value must be a string", "value", value);
    }
    if (typeof(unitName) === "string") {
        const index = names.indexOf(unitName);
        if (index !== -1) { unitName = 3 * index; }
    }
    return parseFixed(value, (unitName != null) ? unitName: 18);
}

The function takes two arguements and one is strigified value, and another 'unitname'. This function is kind of checker, meat is in 'parseFixed' function. And we see that this function is taken from:

import { formatFixed, parseFixed } from "@ethersproject/bignumber";

From 'bignumber', we get to know it is coming from 'fixednumber':

export { formatFixed, FixedFormat, FixedNumber, parseFixed } from "./fixednumber";

export function parseFixed(value: string, decimals?: BigNumberish): BigNumber {

    if (decimals == null) { decimals = 0; }
    const multiplier = getMultiplier(decimals);

    if (typeof(value) !== "string" || !value.match(/^-?[0-9.]+$/)) {
        logger.throwArgumentError("invalid decimal value", "value", value);
    }

    // Is it negative?
    const negative = (value.substring(0, 1) === "-");
    if (negative) { value = value.substring(1); }

    if (value === ".") {
        logger.throwArgumentError("missing value", "value", value);
    }

    // Split it into a whole and fractional part
    const comps = value.split(".");
    if (comps.length > 2) {
        logger.throwArgumentError("too many decimal points", "value", value);
    }

    let whole = comps[0], fraction = comps[1];
    if (!whole) { whole = "0"; }
    if (!fraction) { fraction = "0"; }

    // Trim trailing zeros
    while (fraction[fraction.length - 1] === "0") {
        fraction = fraction.substring(0, fraction.length - 1);
    }

    // Check the fraction doesn't exceed our decimals size
    if (fraction.length > multiplier.length - 1) {
        throwFault("fractional component exceeds decimals", "underflow", "parseFixed");
    }

    // If decimals is 0, we have an empty string for fraction
    if (fraction === "") { fraction = "0"; }

    // Fully pad the string with zeros to get to wei
    while (fraction.length < multiplier.length - 1) { fraction += "0"; }

    const wholeValue = BigNumber.from(whole);
    const fractionValue = BigNumber.from(fraction);

    let wei = (wholeValue.mul(multiplier)).add(fractionValue);

    if (negative) { wei = wei.mul(NegativeOne); }

    return wei;
}

Hope now you understand where is the real body after all the check. If no, here it is:

const wholeValue = BigNumber.from(whole);
    const fractionValue = BigNumber.from(fraction);

    let wei = (wholeValue.mul(multiplier)).add(fractionValue);

    if (negative) { wei = wei.mul(NegativeOne); }

    return wei;

Basically, Bignumber library is used to convert whole and fraction parts of value into into 'bignumber', and then they are added. So all ether calculation is 'wei' in ethers.

But from where the 'Bignumber' is coming? It is coming from:

import { BigNumber, BigNumberish, isBigNumberish } from "./bignumber";

Lol, it is coming from 'bignumber'.

From there, we get to know it is wrapper around 'BN.js' library:

/**
 *  BigNumber
 *
 *  A wrapper around the BN.js object. We use the BN.js library
 *  because it is used by elliptic, so it is required regardless.
 *
 */

import _BN from "bn.js";
import BN = _BN.BN;

Do you still want to go deeper than that. Bravo. Here we go. The 'from' method is written by Ricmoo/team

 static from(value: any): BigNumber {
        if (value instanceof BigNumber) { return value; }

        if (typeof(value) === "string") {
            if (value.match(/^-?0x[0-9a-f]+$/i)) {
                return new BigNumber(_constructorGuard, toHex(value));
            }

            if (value.match(/^-?[0-9]+$/)) {
                return new BigNumber(_constructorGuard, toHex(new BN(value)));
            }

            return logger.throwArgumentError("invalid BigNumber string", "value", value);
        }

If you are still here, understand going below beyond this will push you outside the dev zone of application layer, you will go into decimal conversion mathematics. Your choose!

like it? Then, don't forget to give heart!

How to sell a token programmatically

rahuldev-17 — Wed, 05 Jan 2022 18:27:14 +0000

If you want to sell a token on Binance Smart Chain (BSC) via a script, we present a complete program. You can use the script easily for other EVM compatible blockchains just by modifying the addresses for:

native coin
router
desired token address

MOST IMPORTANT: USE AN ACCOUNT WITH JUST NOMINAL VALUE OF BNB SUCH AS 0.01 BNB WHICH YOU CAN AFFORD TO LOSE. I cannot overemphasis it.

I assume that you have experience with basic nodejs programming, and you have installed 'metamask' wallet, and know the seed phrase of your wallet. Further, assuming you already have purchased the token(to purchase token programmatically read this https://dev.to/rahuldev17/how-to-buy-a-token-programmatically-3plb ), here are the steps to sell a token programmatically:

Create a project folder
create a .env file in your project folder
Write your private information in the .env file; do not enclose info in ""; save the file
create another file in the same project folder, and copy paste the 'sellToken.js' script
Put the token address you want to sell for in this file.
execute the script
I have not handled 'returned promise rejections' in this program.

If it is your first time of selling of this token, do approve the token for swapping via 'metamask' if not done beforehand, otherwise you might not be able to sell the token.

'.env' file:

MNEMONIC=
MY_ACCOUNT_ADDRESS=
GET_BLOCK_API_KEY=

'sellToken.js' script:

const ethers = require('ethers');
require('dotenv').config()

const addresses = {
    WBNB: "0xbb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c",// native coin
    router:"0x10ED43C718714eb63d5aA57B78B54704E256024E", // PCS router

    recipient: process.env.MY_ACCOUNT_ADDRESS, //metamask acccount address
    tokenAddress:"" // token address you are interested in 
}


const mnemonic = process.env.MNEMONIC // seed phrase for Metamask 
const mygasPrice = ethers.utils.parseUnits('10', 'gwei');// setting gas price


const provider = new ethers.providers.WebSocketProvider("wss://bsc.getblock.io/testnet/?api_key=" + process.env.GET_BLOCK_API_KEY);
const wallet = ethers.Wallet.fromMnemonic(mnemonic);
const account = wallet.connect(provider);

var amount; 

const router = new ethers.Contract(
  addresses.router,
  [
  'function swapExactTokensForETH(uint256 amountIn, uint256 amountOutMin, address[] path, address to, uint256 deadline)',
      'function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)     external     payable     returns (uint[] memory amounts)',
    'function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts)'

  ],
  account
);


const sell = async () => {


    let tokenIn = addresses.tokenAddress , tokenOut = addresses.WBNB;

    const amountIn = ethers.utils.parseUnits("1.0",9); //selling one token with 9 decimals; change decimals to 18 if desired
    const amounts = await router.getAmountsOut(amountIn, [tokenIn, tokenOut]);
    //let us be ready to accept little less of BNB due to price fluctuations
    const amountOutMin = amounts[1].sub(amounts[1].div(10));

    console.log(`
      selling new token
      =================
      tokenIn: ${amountIn} ${tokenIn}
      tokenOut: ${amountOutMin} ${tokenOut} (WBNB)
    `);

    const tx = await router.swapExactTokensForETH(
      amountIn,
      amountOutMin,
      [tokenIn, tokenOut],
      addresses.recipient,
      Math.floor(Date.now() / 1000) + 60 * 15, // 15 minutes from the current Unix time
      {
          gasPrice: mygasPrice,
          gasLimit: 250000
      }
    );

    const receipt = await tx.wait(); 
    console.log('Transaction receipt');
    console.log(receipt);
  }

sell();

Hope you find this useful. If so, give love and share.

How to buy a token programmatically

rahuldev-17 — Wed, 05 Jan 2022 17:36:21 +0000

If you want to buy a token on Binance Smart Chain (BSC) via a script, we present a complete program. You can use the script easily for other EVM compatible blockchains just by modifying the addresses for:

native coin
router and factory
desired token address

MOST IMPORTANT: USE AN ACCOUNT WITH JUST NOMINAL VALUE OF BNB SUCH AS 0.01 BNB WHICH YOU CAN AFFORD TO LOSE. I cannot overemphasis it.

Assuming you have experience with basic nodejs programming, and you have installed 'metamask' wallet, and know the seed phrase, here are the steps to buy a token programmatically:

Create a project folder
create a .env file in your project folder
Write your private information in the .env file; do not enclose info in ""; save the file
create another file in the same project folder, and copy paste the 'buyToken.js' script
Put the token address you want to purchase for in this file.
execute the script

I have not handled 'returned promise rejections' in this program. If it is your first purchase of the token, do import the token in 'metamask' if not done beforehand, otherwise you might not see the token in your account.

'.env' file:

MNEMONIC=
MY_ACCOUNT_ADDRESS=
GET_BLOCK_API_KEY=

'buyToken.js' script:

const ethers = require('ethers');
require('dotenv').config()

const addresses = {
    WBNB: "0xbb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c",// native coin
    router:"0x10ED43C718714eb63d5aA57B78B54704E256024E", // PCS router
    recipient: process.env.MY_ACCOUNT_ADDRESS, //metamask acccount address
    tokenAddress:"" // token address you are interested in 
}


const mnemonic = process.env.MNEMONIC // seed phrase for Metamask 
const mygasPrice = ethers.utils.parseUnits('10', 'gwei');// setting gas price


const provider = new ethers.providers.WebSocketProvider("wss://bsc.getblock.io/testnet/?api_key=" + process.env.GET_BLOCK_API_KEY);
const wallet = ethers.Wallet.fromMnemonic(mnemonic);
const account = wallet.connect(provider);

var amount; 

const router = new ethers.Contract(
  addresses.router,
  [
  'function swapExactTokensForETH(uint256 amountIn, uint256 amountOutMin, address[] path, address to, uint256 deadline)',
      'function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)     external     payable     returns (uint[] memory amounts)',
    'function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts)'

  ],
  account
);


  const buy = async () => {

  let tokenIn = addresses.WBNB , tokenOut = addresses.tokenAddress;

  const amountIn = ethers.utils.parseUnits('0.0001', 'ether'); // Most Important.. swapping only 0.0001 BNB, change this value if desired
  const amounts = await router.getAmountsOut(amountIn, [tokenIn, tokenOut]);
  // accepting a little lower amount 
  const amountOutMin = amounts[1].sub(amounts[1].div(10));

  // to be used later while selling : amount = amountOutMin;

  console.log(`
    Buying new token
    =================
    tokenIn: ${amountIn} ${tokenIn} (WBNB)
    tokenOut: ${amountOutMin} ${tokenOut}
  `);

   const tx = await router.swapExactETHForTokens( 
    amountOutMin,
    [tokenIn, tokenOut],
    addresses.recipient,
    Math.floor(Date.now() / 1000) + 60 * 15, // 15 minutes from the current Unix time
    {
        gasPrice: mygasPrice,
        gasLimit: 270000, 
        value: amountIn // important for exact ethereum amount
    },

  );
  const receipt = await tx.wait(); 
  console.log('Transaction receipt');
  console.log(receipt); 
}
buy();

Hope you find this useful. If so, give love and share.

How to deploy a solidity contract with etherjs

rahuldev-17 — Wed, 29 Dec 2021 16:40:05 +0000

Assuming you have installed metamask, and know the seed phrase, here are steps to deploy contract using 'ethers' and 'fs':

compile the contract to .bin and .abi files
load 'ethers' and 'fs'
create a 'signer' object using 'provider', 'Wallet', and 'connect' methods from 'ethers'
create a contract instance from 'ContractFactory' method
use deploy method as promise
Here I have used 'getblock' as web3 provider for example (see https://getblock.io/docs/get-started/auth-with-api-key/). Other alternatives are 'quicknode', 'alchemy' and 'infura'.

We will deploy the code to the BSC testnet, but same procedure will apply for other Ethereum Virtual Machine(EVM) compatible chains, such as : Avalanche Contract Chain (C-Chain), Binance Smart Chain (BSC) mainnet, Fantom Opera and Polygon etc.

nodejs script for contract deployment goes here:

//load 'ethers' and 'fs'

ethers = require('ethers');
fs = require('fs');

//Read bin and abi file to object; names of the solcjs-generated files renamed
bytecode = fs.readFileSync('storage.bin').toString();
abi = JSON.parse(fs.readFileSync('storage.abi').toString());

//to create 'signer' object;here 'account'
const mnemonic = "<see-phrase>" // seed phrase for your Metamask account
const provider = new ethers.providers.WebSocketProvider("wss://bsc.getblock.io/testnet/?api_key=<your-api-key>");
const wallet = ethers.Wallet.fromMnemonic(mnemonic);
const account = wallet.connect(provider);

const myContract = new ethers.ContractFactory(abi, bytecode, account);

//Using 'deploy method 'in 'async-await' 
async function main() {
// If your contract requires constructor args, you can specify them here
const contract = await myContract.deploy();

console.log(contract.address);
console.log(contract.deployTransaction);
}

main();

In the above code, 'account' is the 'signer' of the ethers docs
https://docs.ethers.io/v5/api/contract/contract-factory/#ContractFactory--creating

ethers.ContractFactory( interface , bytecode [ , signer ] )

Do not hesitate to ask in discussion if you face any problem in deploying your contract.

How to understand long contracts with a visual tool: Sol2Uml

rahuldev-17 — Sun, 26 Dec 2021 03:04:08 +0000

Have you ever faced difficulty in understanding a large solidity contract? If you answer in affirmative, you are in good company. Commercially deployed contracts on mainnet typically runs in ~800 to 1000 LOC. To wrap your brain around the whole contract just by scrolling might not be so useful. So let us explore a visual aid for this purpose: "Solidity to UML".

Let us first see its example on BSC scan (blockchain explorer-mainnet). On the contract page, click the on the "outline" button to get an overview of different interfaces, library and available abstract contracts(zoom in the image for clarity).

To get a visual representation click on the "more options" dropdown list, and click on the "Sol2Uml" button(zoom in the image for clarity).

A vector file(SVG) is generated which can be zoomed infinitely to view the call diagrams between class like structures of your contracts.

You can also use it to view contracts in your local environment by installing it as npm package. See details here.

Comment or ask if any further queries down below the box.