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::storagecontrol_v2::StorageControlClient(
google::cloud::storagecontrol_v2::MakeStorageControlConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 the default authentication credentials used by client libraries when interacting with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available is 2.37.0-rc, with a list of versions dating back to 2.21.0 accessible via links.\u003c/p\u003e\n"],["\u003cp\u003eOverriding default credentials can be done using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated in the provided C++ example code, which loads a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eFor managing service account keys, it is recommended to consult the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"],["\u003cp\u003eAdditional information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the "Authentication Components" documentation.\u003c/p\u003e\n"]]],[],null,[]]
