func processOptions(env string) {
field:
	for env != "" {
		field := ""
		i := indexByte(env, ',')
		if i < 0 {
			field, env = env, ""
		} else {
			field, env = env[:i], env[i+1:]
		}
		if len(field) < 4 || field[:4] != "cpu." {
			continue
		}
		i = indexByte(field, '=')
		if i < 0 {
			print("GODEBUG: no value specified for \"", field, "\"\n")

// limitations under the License.

package features

import (
	"time"

	"istio.io/istio/pkg/env"
	"istio.io/istio/pkg/log"
)

// Define telemetry related features here.
var (
	traceSamplingVar = env.Register(
		"PILOT_TRACE_SAMPLING",
		1.0,
		"Sets the mesh-wide trace sampling percentage. Should be 0.0 - 100.0. Precision to 0.01. "+
			"Default is 1.0.",
	)

			"If unset fallbacks to ETCD_CREDS env.")
}

func lookupEnv(env string) (string, error) {
	result, ok := os.LookupEnv(env)
	if !ok || len(result) == 0 {
		return result, fmt.Errorf("%s variable unset - expected failure", env)
	}
	return result, nil
}

func fallbackToEnv(flag, env string) (string, error) {
	klog.Infof("--%s unset - falling back to %s variable", flag, env)
	return lookupEnv(env)
}

  const absl::Status write_status =
      WriteStringToFile(dst_file_path, "test_string");
  ASSERT_THAT(write_status, IsOk());

  auto* const env = tsl::Env::Default();
  ASSERT_THAT(env->FileExists(dst_file_path), IsOk());

  std::string data{};
  ASSERT_THAT(tsl::ReadFileToString(env, dst_file_path, &data), IsOk());

  EXPECT_THAT(data, Eq("test_string"));
}

TEST(IoTest, ReadFileToString) {

env TESTGO_VERSION=go1.500
env TESTGO_VERSION_SWITCH=mismatch

# go env GOMOD should not trigger a toolchain download
cd $GOPATH/mod
go env GOMOD
stdout mod[/\\]go.mod
! stderr 'go: toolchain go1.500 invoked to provide go1.700'

# go env GOWORK should not trigger a toolchain download
cd $GOPATH/work
go env GOWORK
stdout work[/\\]go.work
! stderr 'go: toolchain go1.500 invoked to provide go1.700'

-- $GOPATH/mod/go.mod --

func mustCreateEnv(t testing.TB, envOptions ...cel.EnvOption) *cel.Env {
	envSet, err := environment.MustBaseEnvSet(environment.DefaultCompatibilityVersion(), true).
		Extend(environment.VersionedOptions{
			IntroducedVersion: version.MajorMinor(1, 30),
			EnvOptions:        envOptions,
		})
	if err != nil {
		t.Fatalf("fail to create env set: %v", err)
	}
	env, err := envSet.Env(environment.StoredExpressions)
	if err != nil {

		},
	}

	configStore := memory.Make(collections.Pilot)

	env := model.NewEnvironment()
	env.ServiceDiscovery = serviceDiscovery
	env.ConfigStore = configStore
	env.Watcher = mesh.NewFixedWatcher(meshConfig)

	pushContext := model.NewPushContext()
	env.Init()
	_ = pushContext.InitContext(env, nil, nil)
	env.SetPushContext(pushContext)
	pushContext.SetDestinationRulesForTesting([]config.Config{
		{

	"istio.io/istio/pkg/config/constants"
	"istio.io/istio/pkg/env"
)

var (
	PodNamespace      = env.RegisterStringVar("POD_NAMESPACE", "", "pod's namespace").Get()
	SystemNamespace   = env.RegisterStringVar("SYSTEM_NAMESPACE", constants.IstioSystemNamespace, "istio system namespace").Get()
	PodName           = env.RegisterStringVar("POD_NAME", "", "").Get()
	NodeName          = env.RegisterStringVar("NODE_NAME", "", "").Get()

)

// registerAmbient registers a variable that is allowed only if EnableAmbient is set
func registerAmbient[T env.Parseable](name string, defaultWithAmbient, defaultWithoutAmbient T, description string) T {
	if EnableAmbient {
		return env.Register(name, defaultWithAmbient, description).Get()
	}

	_, f := env.Register(name, defaultWithoutAmbient, description).Lookup()
	if f {

	delay := env.Get(EnvDelayLegacy, "")
	if delay == "" {
		delay = env.Get(EnvDelay, kvs.GetWithDefault(Delay, DefaultKVS))
	}
	cfg.Delay, err = strconv.ParseFloat(delay, 64)
	if err != nil {
		return err
	}
	maxWait := env.Get(EnvMaxWaitLegacy, "")
	if maxWait == "" {
		maxWait = env.Get(EnvMaxWait, kvs.GetWithDefault(MaxWait, DefaultKVS))
	}