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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 provides documentation for overriding default authentication credentials when interacting with Google Cloud Services using the C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version is 2.37.0-rc, with the current documentation focusing on version 2.33.0 and older releases back to 2.21.0, each with their own documentation link.\u003c/p\u003e\n"],["\u003cp\u003eBy utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, developers can override default authentication to provide their preferred method of authentication, such as loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe example illustrates the manual loading of service account credentials from a key file, but it's important to consult the best practices guide for managing service account keys.\u003c/p\u003e\n"],["\u003cp\u003eFurther details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the "Authentication Components" section of the documentation.\u003c/p\u003e\n"]]],[],null,[]]
