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utils/renameio/example_test.go

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+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package renameio_test
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/safing/portbase/utils/renameio"
+)
+
+func ExampleTempFile_justone() {
+	persist := func(temperature float64) error {
+		t, err := renameio.TempFile("", "/srv/www/metrics.txt")
+		if err != nil {
+			return err
+		}
+		defer t.Cleanup()
+		if _, err := fmt.Fprintf(t, "temperature_degc %f\n", temperature); err != nil {
+			return err
+		}
+		return t.CloseAtomicallyReplace()
+	}
+	// Thanks to the write package, a webserver exposing /srv/www never
+	// serves an incomplete or missing file.
+	if err := persist(31.2); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleTempFile_many() {
+	// Prepare for writing files to /srv/www, effectively caching calls to
+	// TempDir which TempFile would otherwise need to make.
+	dir := renameio.TempDir("/srv/www")
+	persist := func(temperature float64) error {
+		t, err := renameio.TempFile(dir, "/srv/www/metrics.txt")
+		if err != nil {
+			return err
+		}
+		defer t.Cleanup()
+		if _, err := fmt.Fprintf(t, "temperature_degc %f\n", temperature); err != nil {
+			return err
+		}
+		return t.CloseAtomicallyReplace()
+	}
+
+	// Imagine this was an endless loop, reading temperature sensor values.
+	// Thanks to the write package, a webserver exposing /srv/www never
+	// serves an incomplete or missing file.
+	for {
+		if err := persist(31.2); err != nil {
+			log.Fatal(err)
+		}
+	}
+}