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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version available is 2.37.0-rc, with numerous other versions from 2.36.0 down to 2.11.0 also being accessible.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries generally use Application Default Credentials for authentication with Google Cloud Services, but it can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eOverriding default credentials can be achieved by providing the UnifiedCredentialsOption, as shown in the example, which allows for the use of a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided code example demonstrates how to load a service account key file using the UnifiedCredentialsOption, although it is considered basic error handling.\u003c/p\u003e\n"],["\u003cp\u003eFor more information, you can consult the "Best practices for managing service account keys" and "Authentication Components" resources.\u003c/p\u003e\n"]]],[],null,[]]
