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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 available version is 2.37.0-rc, with multiple other versions, down to 2.11.0, also listed for reference.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries use Application Default Credentials (ADC) by default for authentication with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication credentials using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as by loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example demonstrates how to load a service account key file for authentication using \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e, but it's suggested to also refer to the best practices guide for managing service account keys.\u003c/p\u003e\n"],["\u003cp\u003eThe Authentication Components link provides information on the factory functions to create \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
