Feature: Add option to log output to file (#246)

cmd/root.go

@@ -116,6 +116,7 @@ func init() {
 	rootCmd.Flags().BoolVar(&config.AllowUntrustedTLS, "allow-untrusted-tls", config.AllowUntrustedTLS, "Do not verify HTTPS certificates (link checker & screenshots)")
 
 	rootCmd.Flags().StringVarP(&config.SMTPCLITags, "tag", "t", config.SMTPCLITags, "Tag new messages matching filters")
+	rootCmd.Flags().StringVar(&logger.LogFile, "log-file", logger.LogFile, "Log output to file instead of stdout")
 	rootCmd.Flags().BoolVarP(&logger.QuietLogging, "quiet", "q", logger.QuietLogging, "Quiet logging (errors only)")
 	rootCmd.Flags().BoolVarP(&logger.VerboseLogging, "verbose", "v", logger.VerboseLogging, "Verbose logging")
 
@@ -223,6 +224,9 @@ func initConfigFromEnv() {
 	if getEnabledFromEnv("MP_ALLOW_UNTRUSTED_TLS") {
 		config.AllowUntrustedTLS = true
 	}
+	if len(os.Getenv("MP_LOG_FILE")) > 0 {
+		logger.LogFile = os.Getenv("MP_LOG_FILE")
+	}
 	if getEnabledFromEnv("MP_QUIET") {
 		logger.QuietLogging = true
 	}

internal/logger/logger.go

@@ -18,6 +18,8 @@ var (
 	QuietLogging bool
 	// NoLogging shows only fatal errors
 	NoLogging bool
+	// LogFile sets a log file
+	LogFile string
 )
 
 // Log returns the logger instance
@@ -36,11 +38,21 @@ func Log() *logrus.Logger {
 			log.SetLevel(logrus.PanicLevel)
 		}
 
-		log.Out = os.Stdout
+		if LogFile != "" {
+			file, err := os.OpenFile(LogFile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0664)
+			if err == nil {
+				log.Out = file
+			} else {
+				log.Out = os.Stdout
+				log.Warn("Failed to log to file, using default stderr")
+			}
+		} else {
+			log.Out = os.Stdout
+		}
+
 		log.SetFormatter(&logrus.TextFormatter{
 			FullTimestamp:   true,
 			TimestampFormat: "2006/01/02 15:04:05",
-			ForceColors:     true,
 		})
 	}