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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version of the service usage documentation is 2.37.0-rc, with several prior versions available, ranging down to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication for client libraries uses Application Default Credentials, but this can be overridden when necessary.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default credentials using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated with an example showing how to load a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eFor managing service account keys, it's recommended to refer to the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"],["\u003cp\u003eMore information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the Authentication Components section.\u003c/p\u003e\n"]]],[],null,[]]
