Log to /var/log/rttys.log when stdout is a terminal

Signed-off-by: Jianhui Zhao <jianhuizhao329@gmail.com>

go.mod

@@ -22,5 +22,5 @@ require (
 	github.com/rakyll/statik v0.1.6
 	github.com/rifflock/lfshook v0.0.0-20180920164130-b9218ef580f5
 	github.com/sirupsen/logrus v1.4.1
-	golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2 // indirect
+	golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2
 )

main.go

@@ -26,6 +26,7 @@ import (
 	"encoding/hex"
 	"flag"
 	"fmt"
+	"golang.org/x/crypto/ssh/terminal"
 	"io"
 	"os"
 	"runtime"
@@ -48,6 +49,9 @@ type RttysConfig struct {
 }
 
 func init() {
+	if terminal.IsTerminal(int(os.Stdout.Fd())) {
+		return
+	}
 	log.AddHook(lfshook.NewHook("/var/log/rttys.log", &log.TextFormatter{}))
 }