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::osconfig_agentendpoint_v1::AgentEndpointServiceClient(
google::cloud::osconfig_agentendpoint_v1::
MakeAgentEndpointServiceConnection(options));
}
Follow these links to find examples for other *Client classes:
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 document provides guidance on overriding default authentication credentials when interacting with Google Cloud Services using client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version available is 2.37.0-rc, with a wide range of stable versions from 2.11.0 to 2.36.0 also accessible.\u003c/p\u003e\n"],["\u003cp\u003eOverriding the default credentials can be achieved by supplying a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, exemplified by loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe document provides links to examples for \u003ccode\u003eAgentEndpointServiceClient\u003c/code\u003e, \u003ccode\u003eOsConfigServiceClient\u003c/code\u003e, and \u003ccode\u003eOsConfigZonalServiceClient\u003c/code\u003e classes, and offers a link to the best practice guide for managing service account keys.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eAuthentication Components\u003c/code\u003e documentation provides more insight on how to create \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
