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::functions_v1::CloudFunctionsServiceClient(
google::cloud::functions_v1::MakeCloudFunctionsServiceConnection(
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"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThe page provides documentation for overriding default authentication credentials when interacting with Google Cloud Services using C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available is 2.37.0-rc, with a range of versions available down to 2.11.0, while the currently documented version is 2.18.0.\u003c/p\u003e\n"],["\u003cp\u003eOverriding the default Application Default Credentials can be done by utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, and this process is illustrated using an example of loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eSpecific examples for \u003ccode\u003efunctions_v1::CloudFunctionsServiceClient\u003c/code\u003e and \u003ccode\u003efunctions_v2::FunctionServiceClient\u003c/code\u003e are also provided, demonstrating the application of custom credentials in different contexts.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eAuthentication Components\u003c/code\u003e link provides further information on the factory functions for creating credentials objects.\u003c/p\u003e\n"]]],[],null,[]]
