// empty string rather than unset (NULL).  Handle that case.
  const char* const env = getenv(name);
  return (env != NULL && env[0] != '\0') ? env : NULL;
#else
  return getenv(name);
#endif
}

#ifdef _MSC_VER
# pragma warning(pop)  // Restores the warning state.
#endif

#if GTEST_OS_WINDOWS_MOBILE

func defaultGOPATH() string {
	env := "HOME"
	if runtime.GOOS == "windows" {
		env = "USERPROFILE"
	} else if runtime.GOOS == "plan9" {
		env = "home"
	}
	if home := os.Getenv(env); home != "" {
		def := filepath.Join(home, "go")
		if filepath.Clean(def) == filepath.Clean(runtime.GOROOT()) {
			// Don't set the default GOPATH to GOROOT,
			// as that will trigger warnings from the go tool.

            String value = entry.getValue();
            gradleInvocation.implicitLauncherJvmArgs.add(String.format("-D%s=%s", key, value));
        }
        if (isDebugLauncher()) {
            if (System.getenv().containsKey("CI")) {
                throw new IllegalArgumentException("Builds cannot be started with the debugger enabled on CI. This will cause tests to hang forever. Remove the call to startLauncherInDebugger().");
            }

The logic in the predicate is opaque to the configuration cache, so all environment variables are considered inputs.
One way to reduce the number of inputs is to always use methods that query a concrete variable name, such as `getenv(String)`, or `getenv().get()`:

====
include::sample[dir="snippets/valueProviders/envVarsSysPropsDo/kotlin",files="build.gradle.kts[]"]
include::sample[dir="snippets/valueProviders/envVarsSysPropsDo/groovy",files="build.gradle[]"]

		switch op {
		default:
			if cache.DebugTest {
				fmt.Fprintf(os.Stderr, "testcache: %s: input list malformed (%q)\n", a.Package.ImportPath, line)
			}
			return cache.ActionID{}, errBadTestInputs
		case "getenv":
			fmt.Fprintf(h, "env %s %x\n", name, hashGetenv(name))
		case "chdir":
			pwd = name // always absolute
			fmt.Fprintf(h, "chdir %s %x\n", name, hashStat(name))
		case "stat":
			if !filepath.IsAbs(name) {

	}
}

func getNetworkName(hnsNetworkName string) (string, error) {
	if len(hnsNetworkName) == 0 {
		klog.V(3).InfoS("Flag --network-name not set, checking environment variable")
		hnsNetworkName = os.Getenv("KUBE_NETWORK")
		if len(hnsNetworkName) == 0 {
			return "", fmt.Errorf("Environment variable KUBE_NETWORK and network-flag not initialized")
		}
	}
	return hnsNetworkName, nil
}

		return
	}

	db, err := gorm.Open(postgres.Open(postgresDSN), &gorm.Config{PrepareStmt: true})
	if err != nil {
		t.Errorf("Open err:%v", err)
	}
	if debug := os.Getenv("DEBUG"); debug == "true" {
		db.Logger = db.Logger.LogMode(logger.Info)
	} else if debug == "false" {
		db.Logger = db.Logger.LogMode(logger.Silent)
	}

	type Object1 struct {
		ID uint
	}

	}
	return r, b
}

// TestLinuxSendfileChild isn't a real test. It's used as a helper process
// for TestLinuxSendfile.
func TestLinuxSendfileChild(*testing.T) {
	if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
		return
	}
	defer os.Exit(0)
	fd3 := os.NewFile(3, "ephemeral-port-listener")
	ln, err := net.FileListener(fd3)
	if err != nil {
		panic(err)
	}

// an error if it does not.
func checkGCCBaseCmd() ([]string, error) {
	// Use $CC if set, since that's what the build uses.
	value := os.Getenv("CC")
	if value == "" {
		// Try $GCC if set, since that's what we used to use.
		value = os.Getenv("GCC")
	}
	if value == "" {
		value = defaultCC(goos, goarch)
	}
	args, err := quoted.Split(value)
	if err != nil {
		return nil, err
	}

		// so it wouldn't be useful to log when that occurs (because it happens in
		// normal operation all the time).
		readModGraphDebugOnce.Do(func() {
			for _, f := range strings.Split(os.Getenv("GODEBUG"), ",") {
				switch f {
				case "lazymod=log":
					debug.PrintStack()
					fmt.Fprintf(os.Stderr, "go: read full module graph.\n")
				case "lazymod=strict":
					debug.PrintStack()