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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 version available is 2.37.0-rc, with multiple versions available from 2.36.0 down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries generally utilize Application Default Credentials for authenticating with Google Cloud Services, but this default can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eYou can override default credentials by supplying a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as exemplified through the loading of a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples on overriding authentication credentials are provided 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\u003eFor further details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, refer to the Authentication Components section.\u003c/p\u003e\n"]]],[],null,[]]
