diff --git a/csv/encoder.go b/csv/encoder.go
index 8616496..a52df98 100644
--- a/csv/encoder.go
+++ b/csv/encoder.go
@@ -18,6 +18,7 @@ package csv
 import (
 	"encoding/csv"
 	"io"
+	"strconv"
 
 	"github.com/booster-proj/lsaddr/lookup"
 )
@@ -37,13 +38,18 @@ func NewEncoder(w io.Writer) *Encoder {
 // Encode writes `l` into encoder's writer in CSV format. Some data may have been
 // written to the writer even upon error.
 func (e *Encoder) Encode(l []lookup.NetFile) error {
-	header := []string{"COMMAND", "NET", "SRC", "DST"}
+	header := []string{"PID", "NET", "SRC", "DST"}
 	if err := e.w.Write(header); err != nil {
 		return err
 	}
 
 	for _, v := range l {
-		record := []string{v.Command, v.Src.Network(), v.Src.String(), v.Dst.String()}
+		record := []string{
+			strconv.Itoa(v.Pid),
+			v.Src.Network(),
+			v.Src.String(),
+			v.Dst.String(),
+		}
 		if err := e.w.Write(record); err != nil {
 			return err
 		}
diff --git a/csv/encoder_test.go b/csv/encoder_test.go
index 4828e92..7b5ca2c 100644
--- a/csv/encoder_test.go
+++ b/csv/encoder_test.go
@@ -32,9 +32,9 @@ func TestEncode_CSV(t *testing.T) {
 		t.Fatalf("Unexpected error: %v", err)
 	}
 
-	expOut := `COMMAND,NET,SRC,DST
-foo,udp,192.168.0.61:54104,52.94.218.7:443
-bar,udp,[::1]:60051,[::1]:60052
+	expOut := `PID,NET,SRC,DST
+101,udp,192.168.0.61:54104,52.94.218.7:443
+102,udp,[::1]:60051,[::1]:60052
 `
 	if expOut != w.String() {
 		t.Fatalf("Unexpected output: wanted \"%s\", found \"%s\"", expOut, w.String())
@@ -42,8 +42,8 @@ bar,udp,[::1]:60051,[::1]:60052
 }
 
 var netFiles0 = []lookup.NetFile{
-	{"foo", newUDPAddr("192.168.0.61:54104"), newUDPAddr("52.94.218.7:443")},
-	{"bar", newUDPAddr("[::1]:60051"), newUDPAddr("[::1]:60052")},
+	{101, newUDPAddr("192.168.0.61:54104"), newUDPAddr("52.94.218.7:443")},
+	{102, newUDPAddr("[::1]:60051"), newUDPAddr("[::1]:60052")},
 }
 
 func newUDPAddr(address string) net.Addr {