Add LogToOutput, a one-stop shop for writing logs to a io.Writer

klog.go

@@ -803,6 +803,16 @@ func SetOutputBySeverity(name string, w io.Writer) {
 	logging.file[sev] = rb
 }
 
+// LogToOutput configures klog to output to the specified writer. It is equivalent to SetOutput()
+// and flag.Set("logtostderr", "false")
+func LogToOutput(w io.Writer) {
+	SetOutput(w)
+	logging.mu.Lock()
+	defer logging.mu.Unlock()
+
+	logging.toStderr = false
+}
+
 // output writes the data to the log files and releases the buffer.
 func (l *loggingT) output(s severity, log logr.InfoLogger, buf *buffer, file string, line int, alsoToStderr bool) {
 	l.mu.Lock()

klog_test.go

@@ -351,6 +351,19 @@ func TestSetOutputDataRace(t *testing.T) {
 	}
 }
 
+func TestLogToOutput(t *testing.T) {
+	defer logging.swap(logging.newBuffers())
+	buf := new(bytes.Buffer)
+	LogToOutput(buf)
+
+	Info("Does LogToOutput work?")
+
+	str := buf.String()
+	if !strings.Contains(str, "Does LogToOutput work?") {
+		t.Fatalf("Expected %s to contain \"Does LogToOutput work?\"", str)
+	}
+}
+
 // vGlobs are patterns that match/don't match this file at V=2.
 var vGlobs = map[string]bool{
 	// Easy to test the numeric match here.