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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-07-02 UTC."],[[["This page provides documentation for overriding default authentication credentials when using Google Cloud client libraries, specifically focusing on how to utilize `UnifiedCredentialsOption`."],["The most recent release candidate version is 2.37.0-rc, and a range of previous versions are also listed, spanning from 2.36.0 back to 2.11.0."],["An example demonstrates how to load a service account key file using `UnifiedCredentialsOption`, and it is mentioned that this can be done for the `AgentEndpointServiceClient`, `OsConfigServiceClient`, and `OsConfigZonalServiceClient`."],["Application Default Credentials are used to authenticate with Google Cloud Services, but it can be overriden in some cases, which is the main content of the documentation."],["For more information about managing service account keys, the documentation recommends consulting the [Best practices for managing service account keys](https://cloud.google.com/iam/docs/best-practices-for-managing-service-account-keys) guide."]]],[]]
