Per suggestions

internal/common/common_unix.go

@@ -3,14 +3,11 @@
 package common
 
 import (
-	"errors"
 	"os/exec"
 	"strconv"
 	"strings"
 )
 
-var ErrorNoChildren = errors.New("Process does not have children or does not exist")
-
 func CallLsof(invoke Invoker, pid int32, args ...string) ([]string, error) {
 	var cmd []string
 	if pid == 0 { // will get from all processes.
@@ -51,7 +48,7 @@ func CallPgrep(invoke Invoker, pid int32) ([]int32, error) {
 	}
 	out, err := invoke.Command(pgrep, cmd...)
 	if err != nil {
-		return []int32{}, ErrorNoChildren
+		return []int32{}, err
 	}
 	lines := strings.Split(string(out), "\n")
 	ret := make([]int32, 0, len(lines))

process/process_linux.go

@@ -19,7 +19,7 @@ import (
 	"github.com/shirou/gopsutil/net"
 )
 
-var ErrorNoChildren = errors.New("Process does not have children")
+var ErrorNoChildren = errors.New("process does not have children")
 
 const (
 	PrioProcess = 0 // linux/resource.h
@@ -208,7 +208,7 @@ func (p *Process) MemoryPercent() (float32, error) {
 func (p *Process) Children() ([]*Process, error) {
 	pids, err := common.CallPgrep(invoke, p.Pid)
 	if err != nil {
-		if err == common.ErrorNoChildren {
+		if pids == nil || len(pids) == 0 {
 			return nil, ErrorNoChildren
 		}
 		return nil, err