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 2025-04-23 UTC."],[[["The latest version of the documentation for overriding authentication in C++ is 2.37.0-rc, with multiple previous versions also available for reference, ranging from 2.36.0 down to 2.11.0."],["Client libraries typically use Application Default Credentials for Google Cloud Services, but you can override this default by using the `UnifiedCredentialsOption`."],["To override default credentials, you can load a service account key file, as demonstrated in the provided example using `google::cloud::MakeServiceAccountCredentials`."],["Examples of overriding authentication are available for several client classes, such as `iam_admin_v1::IAMClient`, `iam_credentials_v1::IAMCredentialsClient`, `iam_v1::IAMPolicyClient`, and `iam_v2::PoliciesClient`."],["The [Best practices for managing service account keys](https://cloud.google.com/iam/docs/best-practices-for-managing-service-account-keys) guide provides in-depth information about service account key management, and you can also find more information on creating credentials objects by consulting the [Authentication Components](https://cloud.google.com/cpp/docs/reference/common/latest/group__guac.html) documentation."]]],[]]
