Revert "simplify ps command"

This reverts commit 067ce21.

Signed-off-by: Wang Long <long.wanglong@huawei.com>

ps.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"strconv"
 	"strings"
 
 	"github.com/urfave/cli"
@@ -41,28 +42,58 @@ var psCommand = cli.Command{
 			return nil
 		}
 
-		pidlist := []string{}
-		for _, pid := range pids {
-			pidlist = append(pidlist, fmt.Sprintf("%d", pid))
-		}
-
 		// [1:] is to remove command name, ex:
 		// context.Args(): [containet_id ps_arg1 ps_arg2 ...]
 		// psArgs:         [ps_arg1 ps_arg2 ...]
 		//
 		psArgs := context.Args()[1:]
 		if len(psArgs) == 0 {
-			psArgs = []string{"-f"}
+			psArgs = []string{"-ef"}
 		}
 
-		psArgs = append(psArgs, "-p", strings.Join(pidlist, ","))
 		output, err := exec.Command("ps", psArgs...).Output()
 		if err != nil {
 			return err
 		}
 
-		fmt.Printf(string(output))
+		lines := strings.Split(string(output), "\n")
+		pidIndex, err := getPidIndex(lines[0])
+		if err != nil {
+			return err
+		}
+
+		fmt.Println(lines[0])
+		for _, line := range lines[1:] {
+			if len(line) == 0 {
+				continue
+			}
+			fields := strings.Fields(line)
+			p, err := strconv.Atoi(fields[pidIndex])
+			if err != nil {
+				return fmt.Errorf("unexpected pid '%s': %s", fields[pidIndex], err)
+			}
+
+			for _, pid := range pids {
+				if pid == p {
+					fmt.Println(line)
+					break
+				}
+			}
+		}
 		return nil
 	},
 	SkipArgReorder: true,
 }
+
+func getPidIndex(title string) (int, error) {
+	titles := strings.Fields(title)
+
+	pidIndex := -1
+	for i, name := range titles {
+		if name == "PID" {
+			return i, nil
+		}
+	}
+
+	return pidIndex, fmt.Errorf("couldn't find PID field in ps output")
+}