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::servicecontrol_v1::QuotaControllerClient(
google::cloud::servicecontrol_v1::MakeQuotaControllerConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 latest release candidate version is 2.37.0-rc, and the current version displayed on the page is 2.35.0, with several previous versions accessible.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries use Application Default Credentials by default for Google Cloud Services, but this can be overridden using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eYou can load a service account key file explicitly by setting \u003ccode\u003egoogle::cloud::UnifiedCredentialsOption\u003c/code\u003e with service account credentials.\u003c/p\u003e\n"],["\u003cp\u003eThe page provides examples on how to override authentication credentials for \u003ccode\u003eservicecontrol_v1::QuotaControllerClient\u003c/code\u003e, \u003ccode\u003eservicecontrol_v1::ServiceControllerClient\u003c/code\u003e, and \u003ccode\u003eservicecontrol_v2::ServiceControllerClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe page directs you to further resources for authentication components and best practices for managing service account keys.\u003c/p\u003e\n"]]],[],null,[]]
