diff --git a/client/operation.go b/client/operation.go
index 676aaee..cc60987 100644
--- a/client/operation.go
+++ b/client/operation.go
@@ -272,30 +272,65 @@ func (hc *houstonClient) launch(meta *procmeta) error {
 		thisFileSize := 0
 		logFileIndex := 0
 
-		logFileNamePrefix := makeLogFilePrefix(meta, index)
-		logFileName := fmt.Sprintf("%s_%d.log", logFileNamePrefix, logFileIndex)
-		targetFile, err := os.Create(logFileName)
-		if err != nil {
-			logger.Println("failed to create log file :", logFileName)
-			return
-		}
-
-		exef, _ := os.Executable()
-		var linkPath string
-		if index == 0 {
-			linkPath = path.Join(path.Dir(exef), path.Dir(logFileName), meta.name+".log")
-		} else {
-			linkPath = path.Join(path.Dir(exef), path.Dir(logFileName), fmt.Sprintf("%s_%d.log", meta.name, index))
-		}
-
-		os.Remove(linkPath)
-		os.Symlink(path.Base(filepath.ToSlash(targetFile.Name())), linkPath)
-
-		defer func() {
-			if targetFile != nil {
-				targetFile.Close()
+		var logWriter func([]byte)
+		if *logger.UseLogFile {
+			logFileNamePrefix := makeLogFilePrefix(meta, index)
+			logFileName := fmt.Sprintf("%s_%d.log", logFileNamePrefix, logFileIndex)
+			targetFile, err := os.Create(logFileName)
+			if err != nil {
+				logger.Println("failed to create log file :", logFileName)
+				return
 			}
-		}()
+
+			exef, _ := os.Executable()
+			var linkPath string
+			if index == 0 {
+				linkPath = path.Join(path.Dir(exef), path.Dir(logFileName), meta.name+".log")
+			} else {
+				linkPath = path.Join(path.Dir(exef), path.Dir(logFileName), fmt.Sprintf("%s_%d.log", meta.name, index))
+			}
+
+			os.Remove(linkPath)
+			os.Symlink(path.Base(filepath.ToSlash(targetFile.Name())), linkPath)
+
+			defer func() {
+				if targetFile != nil {
+					targetFile.Close()
+				}
+			}()
+
+			logWriter = func(buff []byte) {
+				for written := 0; written < len(buff); {
+					n, err := targetFile.Write(buff)
+					if err != nil {
+						logger.Println("write log file failed :", logFileName, err)
+						break
+					} else {
+						written += n
+						thisFileSize += n
+					}
+				}
+
+				if thisFileSize > 5*1024*1024 {
+					logFileIndex++
+					logFileName = fmt.Sprintf("%s_%d.log", logFileNamePrefix, logFileIndex)
+					nextTargetFile, err := os.Create(logFileName)
+					if err != nil {
+						logger.Println("failed to create log file :", logFileName)
+					} else {
+						targetFile.Close()
+						targetFile = nextTargetFile
+						os.Remove(linkPath)
+						os.Symlink(path.Base(filepath.ToSlash(targetFile.Name())), linkPath)
+						thisFileSize = 0
+					}
+				}
+			}
+		} else {
+			logWriter = func(buff []byte) {
+				os.Stdout.Write(buff)
+			}
+		}
 
 		readingMetric := false
 		var metricBuffer []byte
@@ -362,31 +397,7 @@ func (hc *houstonClient) launch(meta *procmeta) error {
 				continue
 			}
 
-			for written := 0; written < len(buff); {
-				n, err := targetFile.Write(buff)
-				if err != nil {
-					logger.Println("write log file failed :", logFileName, err)
-					break
-				} else {
-					written += n
-					thisFileSize += n
-				}
-			}
-
-			if thisFileSize > 5*1024*1024 {
-				logFileIndex++
-				logFileName = fmt.Sprintf("%s_%d.log", logFileNamePrefix, logFileIndex)
-				nextTargetFile, err := os.Create(logFileName)
-				if err != nil {
-					logger.Println("failed to create log file :", logFileName)
-				} else {
-					targetFile.Close()
-					targetFile = nextTargetFile
-					os.Remove(linkPath)
-					os.Symlink(path.Base(filepath.ToSlash(targetFile.Name())), linkPath)
-					thisFileSize = 0
-				}
-			}
+			logWriter(buff)
 		}
 	}