diff --git a/modules/diferenco/unified_encoder.go b/modules/diferenco/unified_encoder.go
index 39d35d0..a2430dc 100644
--- a/modules/diferenco/unified_encoder.go
+++ b/modules/diferenco/unified_encoder.go
@@ -194,7 +194,7 @@ func (e *UnifiedEncoder) writePatchHunk(b *strings.Builder, hunk *Hunk) {
 		_, _ = b.WriteString(" +")
 		_, _ = b.WriteString(strconv.Itoa(hunk.ToLine))
 	}
-	_, _ = b.WriteString("@@")
+	_, _ = b.WriteString(" @@")
 	_, _ = b.WriteString(e.color.Reset(color.Frag))
 	_ = b.WriteByte('\n')
 	for _, line := range hunk.Lines {
diff --git a/utils/diff2/main.go b/utils/diff2/main.go
new file mode 100644
index 0000000..d458ade
--- /dev/null
+++ b/utils/diff2/main.go
@@ -0,0 +1,47 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/antgroup/hugescm/modules/diferenco"
+	"github.com/antgroup/hugescm/modules/diferenco/color"
+)
+
+func main() {
+	if len(os.Args) < 3 {
+		fmt.Fprintf(os.Stderr, "usage: %s file1 file2\n", os.Args[0])
+		return
+	}
+	fd1, err := os.Open(os.Args[1])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "open file %s error: %v\n", os.Args[1], err)
+		return
+	}
+	defer fd1.Close()
+	fd2, err := os.Open(os.Args[2])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "open file %s error: %v\n", os.Args[2], err)
+		return
+	}
+	defer fd2.Close()
+
+	u, err := diferenco.DoUnified(context.Background(), &diferenco.Options{
+		From: &diferenco.File{
+			Path: os.Args[1],
+		},
+		To: &diferenco.File{
+			Path: os.Args[2],
+		},
+		R1: fd1,
+		R2: fd2,
+	})
+	if err != nil {
+		return
+	}
+	e := diferenco.NewUnifiedEncoder(os.Stderr)
+	e.SetColor(color.NewColorConfig())
+	_ = e.Encode([]*diferenco.Unified{u})
+
+}