function envString(string calldata key) external returns (string value);
function envString(string calldata key, string calldata delimiter) external returns (string[] memory values);


Read an environment variable as string or string[]. In case the environment variable is not defined, Forge will fail with the following error message:

[FAIL. Reason: Failed to get environment variable FOO as type string: environment variable not found]


  • You can put your environment variables in a .env file. Forge will automatically load them when running forge test.
  • For arrays, you can specify the delimiter used to separate the values with the delimiter parameter.
  • Choose a delimiter that doesn't appear in the string values, so that they can be correctly separated.


Single Value

With environment variable STRING_VALUE=hello, world!,

string memory key = "STRING_VALUE";
string memory expected = "hello, world!";
string memory output = vm.envString(key);
assertEq(output, expected);


With environment variable STRING_VALUES=hello, world!|0x7109709ECfa91a80626fF3989D68f67F5b1DD12D;

string memory key = "STRING_VALUES";
string memory delimiter = "|";
string[2] memory expected = [
    "hello, world!",
string[] memory output = vm.envString(key, delimiter);
for (uint i = 0; i < expected.length; ++i) {
    assert(keccak256(abi.encodePacked((output[i]))) == keccak256(abi.encodePacked((expected[i]))));