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::billing_budgets_v1::BudgetServiceClient(
google::cloud::billing_budgets_v1::MakeBudgetServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThis page documents the override authentication feature for Google Cloud C++ client libraries, specifically within the context of billing.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version, 2.37.0-rc, and several prior versions, dating back to 2.11.0, are listed, and the 2.26.0 is highlighted as the main version.\u003c/p\u003e\n"],["\u003cp\u003eAuthentication credentials can be overridden by utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e when constructing client objects, which allows for the explicit loading of a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples of overriding the default authentication are available for \u003ccode\u003ebilling_budgets_v1::BudgetServiceClient\u003c/code\u003e, \u003ccode\u003ebilling_v1::CloudBillingClient\u003c/code\u003e, and \u003ccode\u003ebilling_v1::CloudCatalogClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method relies on Application Default Credentials, and for managing service account keys, the "Best practices for managing service account keys" guide is recommended.\u003c/p\u003e\n"]]],[],null,[]]
