Silent output when talking to a shell

If the output is not a terminal, then assume that we are running
docker-env or podman-env under "eval" or similar shell construct.

So don't output all the interactive information, but only return
the actual exit code for some further troubleshooting (perhaps).

cmd/minikube/cmd/docker-env.go

@@ -260,6 +260,11 @@ var dockerEnvCmd = &cobra.Command{
 			return
 		}
 
+		if !out.IsTerminal(os.Stdout) {
+			out.SetSilent(true)
+			exit.SetShell(true)
+		}
+
 		cname := ClusterFlagValue()
 		co := mustload.Running(cname)
 		driverName := co.CP.Host.DriverName

cmd/minikube/cmd/podman-env.go

@@ -153,6 +153,11 @@ var podmanEnvCmd = &cobra.Command{
 			return
 		}
 
+		if !out.IsTerminal(os.Stdout) {
+			out.SetSilent(true)
+			exit.SetShell(true)
+		}
+
 		cname := ClusterFlagValue()
 		co := mustload.Running(cname)
 		driverName := co.CP.Host.DriverName

pkg/minikube/exit/exit.go

@@ -18,6 +18,7 @@ limitations under the License.
 package exit
 
 import (
+	"fmt"
 	"os"
 	"runtime"
 
@@ -27,6 +28,15 @@ import (
 	"k8s.io/minikube/pkg/minikube/style"
 )
 
+var (
+	shell bool
+)
+
+// SetShell configures if we are doing a shell configuration or not
+func SetShell(s bool) {
+	shell = s
+}
+
 // Message outputs a templated message and exits without interpretation
 func Message(r reason.Kind, format string, args ...out.V) {
 	if r.ID == "" {
@@ -54,7 +64,15 @@ func Message(r reason.Kind, format string, args ...out.V) {
 		out.Error(r, "Exiting due to {{.fatal_code}}: {{.fatal_msg}}", args...)
 	}
 
-	os.Exit(r.ExitCode)
+	Code(r.ExitCode)
+}
+
+// Code will exit with a code
+func Code(code int) {
+	if shell {
+		out.Output(os.Stdout, fmt.Sprintf("false exit code %d\n", code))
+	}
+	os.Exit(code)
 }
 
 // Advice is syntactic sugar to output a message with dynamically generated advice

pkg/minikube/mustload/mustload.go

@@ -20,7 +20,6 @@ package mustload
 import (
 	"fmt"
 	"net"
-	"os"
 
 	"github.com/docker/machine/libmachine"
 	"github.com/docker/machine/libmachine/host"
@@ -175,5 +174,5 @@ func ExampleCmd(cname string, action string) string {
 func exitTip(action string, profile string, code int) {
 	command := ExampleCmd(profile, action)
 	out.Styled(style.Workaround, `To start a cluster, run: "{{.command}}"`, out.V{"command": command})
-	os.Exit(code)
+	exit.Code(code)
 }

pkg/minikube/out/out.go

@@ -50,6 +50,8 @@ import (
 // NOTE: If you do not want colorized output, set MINIKUBE_IN_STYLE=false in your environment.
 
 var (
+	// silent will disable all output, if called from a script. Set using SetSilent()
+	silent bool
 	// outFile is where Out* functions send output to. Set using SetOutFile()
 	outFile fdWriter
 	// errFile is where Err* functions send output to. Set using SetErrFile()
@@ -122,6 +124,11 @@ func String(format string, a ...interface{}) {
 	// Flush log buffer so that output order makes sense
 	klog.Flush()
 
+	if silent {
+		klog.Infof(format, a...)
+		return
+	}
+
 	if outFile == nil {
 		klog.Warningf("[unset outFile]: %s", fmt.Sprintf(format, a...))
 		return
@@ -131,7 +138,13 @@ func String(format string, a ...interface{}) {
 	if spin.Active() {
 		spin.Stop()
 	}
-	_, err := fmt.Fprintf(outFile, format, a...)
+
+	Output(outFile, format, a...)
+}
+
+// Output writes a basic formatted string
+func Output(file fdWriter, format string, a ...interface{}) {
+	_, err := fmt.Fprintf(file, format, a...)
 	if err != nil {
 		klog.Errorf("Fprintf failed: %v", err)
 	}
@@ -152,10 +165,7 @@ func spinnerString(format string, a ...interface{}) {
 	if spin.Active() {
 		spin.Stop()
 	}
-	_, err := fmt.Fprintf(outFile, format, a...)
-	if err != nil {
-		klog.Errorf("Fprintf failed: %v", err)
-	}
+	Output(outFile, format, a...)
 	// Start spinning at the end of the printed line
 	spin.Start()
 }
@@ -194,10 +204,7 @@ func Err(format string, a ...interface{}) {
 	if spin.Active() {
 		spin.Stop()
 	}
-	_, err := fmt.Fprintf(errFile, format, a...)
-	if err != nil {
-		klog.Errorf("Fprint failed: %v", err)
-	}
+	Output(errFile, format, a...)
 }
 
 // ErrLn writes a basic formatted string with a newline to stderr
@@ -234,6 +241,20 @@ func FailureT(format string, a ...V) {
 	ErrT(style.Failure, format, a...)
 }
 
+// IsTerminal returns whether we have a terminal or not
+func IsTerminal(w fdWriter) bool {
+	fd := w.Fd()
+	isT := isatty.IsTerminal(fd)
+	klog.Infof("isatty.IsTerminal(%d) = %v\n", fd, isT)
+	return isT
+}
+
+// SetSilent configures whether output is disabled or not
+func SetSilent(q bool) {
+	klog.Infof("Setting silent to %v", q)
+	silent = q
+}
+
 // SetOutFile configures which writer standard output goes to.
 func SetOutFile(w fdWriter) {
 	klog.Infof("Setting OutFile to fd %d ...", w.Fd())