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::serviceusage_v1::ServiceUsageClient(
google::cloud::serviceusage_v1::MakeServiceUsageConnection(options));
}
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 webpage provides a list of available versions for the C++ Service Usage client library, ranging from version 2.11.0 to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method for the client libraries is Application Default Credentials, but the webpage outlines how to override this with the UnifiedCredentialsOption, such as loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example demonstrates how to load a service account key file using \u003ccode\u003egoogle::cloud::UnifiedCredentialsOption\u003c/code\u003e and \u003ccode\u003egoogle::cloud::MakeServiceAccountCredentials\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation includes a reference to the "Best practices for managing service account keys" guide, emphasizing the importance of proper key management.\u003c/p\u003e\n"],["\u003cp\u003eThe Authentication Components documentation is referenced for details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, which is necessary for authentication.\u003c/p\u003e\n"]]],[],null,[]]