return error when CPUTimes fails on callPs, modify comments on ReadLines

common/common.go

@@ -17,7 +17,7 @@ import (
 
 var NotImplementedError = errors.New("not implemented yet")
 
-// ReadLines reads contents from file and splits them by new line.
+// ReadLines reads contents from a file and splits them by new lines.
 // A convenience wrapper to ReadLinesOffsetN(filename, 0, -1).
 func ReadLines(filename string) ([]string, error) {
 	return ReadLinesOffsetN(filename, 0, -1)

process/process_darwin.go

@@ -215,6 +215,10 @@ func convertCpuTimes(s string) (ret float64, err error) {
 func (p *Process) CPUTimes() (*cpu.CPUTimesStat, error) {
 	r, err := callPs("utime,stime", p.Pid, false)
 
+	if err != nil {
+		return nil, err
+	}
+
 	utime, err := convertCpuTimes(r[0][0])
 	if err != nil {
 		return nil, err