C++

// No tmux failure is thrown. Every call answers with a value that is either
// the result or the reason there isn't one.
const auto sessions = server.sessions();
if (!sessions.has_value()) {
  std::fprintf(stderr, "%s\n", sessions.error().diagnostic.c_str());
  return 1;
}

for (const libtmux::Session& session : *sessions) {
  std::printf("%s has %lld window(s)\n", std::string{session.name()}.c_str(),
              session.window_count());
}