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::functions_v1::CloudFunctionsServiceClient(
google::cloud::functions_v1::MakeCloudFunctionsServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 page details how to override default authentication credentials for Google Cloud Services using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e in the C++ client library.\u003c/p\u003e\n"],["\u003cp\u003eThe most recent version documented is 2.37.0-rc, with a history of versions available down to 2.11.0, each with corresponding documentation for \u003ccode\u003efunctions-override-authentication\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eApplication Default Credentials (ADC) are used by default, but you can supply a service account key file to override this behavior, as shown in the code example.\u003c/p\u003e\n"],["\u003cp\u003eFor advanced usage, the page links to documentation on best practices for managing service account keys and the \u003ccode\u003eAuthentication Components\u003c/code\u003e for creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"],["\u003cp\u003eThe example shows how to load a service account key file using an input file stream, which then can be used to create a \u003ccode\u003eCloudFunctionsServiceClient\u003c/code\u003e.\u003c/p\u003e\n"]]],[],null,[]]
