✅Remappings

Solmate (forge remappings)

Install solmate:

forge install rari-capital/solmate

Create an ERC20 contract:

pragma solidity ^0.8.17;

import "solmate/tokens/ERC20.sol";

contract Token is ERC20("name", "symbol", 18) {}

Build:

forge build

See what libraries have been installed:

$ forge remappings

ds-test/=lib/forge-std/lib/ds-test/src/
forge-std/=lib/forge-std/src/
solmate/=lib/solmate/src/

Here solmate is remapped to lib/solmate/src/.

OpenZeppelin Contracts (remappings.txt)

Some libraries, such as OpenZeppelin contracts, should be installed via npm:

mkdir node_modules && npm i @openzeppelin/contracts

We run mkdir first because node modules can be install locally or globally. Reference:

npm install module in current directoryStack Overflow

In contract, import OpenZeppelin Ownable:

import "@openzeppelin/contracts/access/Ownable.sol";

We have to create a remappings.txt file for this import statement to make sense:

@openzeppelin/=node_modules/@openzeppelin

Update our contract:

pragma solidity ^0.8.17;

import "solmate/tokens/ERC20.sol";

contract Token is ERC20("name", "symbol", 18) {}

import "@openzeppelin/contracts/access/Ownable.sol";

contract TestOz is Ownable {}

Build it:

forge build

Build succeeded