Unless otherwise configured, the client libraries use Application Default Credentials to authenticate with Google Cloud Services. While this works for most applications, in some cases you may need to override this default. You can do so by providing the UnifiedCredentialsOption The following example shows how to explicitly load a service account key file:
[](std::string const& keyfile) {
auto is = std::ifstream(keyfile);
is.exceptions(std::ios::badbit); // Minimal error handling in examples
auto contents = std::string(std::istreambuf_iterator<char>(is.rdbuf()), {});
auto options =
google::cloud::Options{}.set<google::cloud::UnifiedCredentialsOption>(
google::cloud::MakeServiceAccountCredentials(contents));
return google::cloud::iam_admin_v1::IAMClient(
google::cloud::iam_admin_v1::MakeIAMConnection(options));
}
Follow these links to find examples for other *Client classes:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-03-21 UTC."],[[["The latest release candidate version is 2.37.0-rc, and the current version displayed on the page is 2.34.0."],["The document provides a comprehensive list of previous versions ranging from 2.36.0 down to 2.11.0, all related to overriding IAM authentication."],["The default authentication method uses Application Default Credentials, but it can be overridden using the `UnifiedCredentialsOption`, such as loading a service account key file."],["Examples are available for multiple `*Client` classes, such as `iam_admin_v1::IAMClient`, `iam_credentials_v1::IAMCredentialsClient`, `iam_v1::IAMPolicyClient`, and `iam_v2::PoliciesClient`, all at version 2.34.0."],["The \"Best practices for managing service account keys\" guide is referenced for further information, as well as the \"Authentication Components\" for more details on `google::cloud::Credentials` objects."]]],[]]