add a reliable way to get fields from /prod/PID/stat

v3/process/process_linux.go

@@ -979,28 +979,24 @@ func (p *Process) fillFromTIDStatWithContext(ctx context.Context, tid int32) (ui
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
-	fields := strings.Fields(string(contents))
-
-	i := 1
-	for !strings.HasSuffix(fields[i], ")") {
-		i++
-	}
+	// Indexing from one, as described in `man proc` about the file /proc/[pid]/stat
+	fields := splitProcStat(contents)
 
-	terminal, err := strconv.ParseUint(fields[i+5], 10, 64)
+	terminal, err := strconv.ParseUint(fields[7], 10, 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
 
-	ppid, err := strconv.ParseInt(fields[i+2], 10, 32)
+	ppid, err := strconv.ParseInt(fields[4], 10, 32)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
-	utime, err := strconv.ParseFloat(fields[i+12], 64)
+	utime, err := strconv.ParseFloat(fields[14], 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
 
-	stime, err := strconv.ParseFloat(fields[i+13], 64)
+	stime, err := strconv.ParseFloat(fields[15], 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
@@ -1008,7 +1004,7 @@ func (p *Process) fillFromTIDStatWithContext(ctx context.Context, tid int32) (ui
 	// There is no such thing as iotime in stat file.  As an approximation, we
 	// will use delayacct_blkio_ticks (aggregated block I/O delays, as per Linux
 	// docs).  Note: I am assuming at least Linux 2.6.18
-	iotime, err := strconv.ParseFloat(fields[i+40], 64)
+	iotime, err := strconv.ParseFloat(fields[42], 64)
 	if err != nil {
 		iotime = 0 // Ancient linux version, most likely
 	}
@@ -1021,14 +1017,14 @@ func (p *Process) fillFromTIDStatWithContext(ctx context.Context, tid int32) (ui
 	}
 
 	bootTime, _ := common.BootTimeWithContext(ctx)
-	t, err := strconv.ParseUint(fields[i+20], 10, 64)
+	t, err := strconv.ParseUint(fields[22], 10, 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
 	ctime := (t / uint64(clockTicks)) + uint64(bootTime)
 	createTime := int64(ctime * 1000)
 
-	rtpriority, err := strconv.ParseInt(fields[i+16], 10, 32)
+	rtpriority, err := strconv.ParseInt(fields[18], 10, 32)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
@@ -1043,19 +1039,19 @@ func (p *Process) fillFromTIDStatWithContext(ctx context.Context, tid int32) (ui
 	snice, _ := unix.Getpriority(prioProcess, int(pid))
 	nice := int32(snice) // FIXME: is this true?
 
-	minFault, err := strconv.ParseUint(fields[i+8], 10, 64)
+	minFault, err := strconv.ParseUint(fields[10], 10, 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
-	cMinFault, err := strconv.ParseUint(fields[i+9], 10, 64)
+	cMinFault, err := strconv.ParseUint(fields[11], 10, 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
-	majFault, err := strconv.ParseUint(fields[i+10], 10, 64)
+	majFault, err := strconv.ParseUint(fields[12], 10, 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
-	cMajFault, err := strconv.ParseUint(fields[i+11], 10, 64)
+	cMajFault, err := strconv.ParseUint(fields[13], 10, 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
 	}
@@ -1121,3 +1117,16 @@ func readPidsFromDir(path string) ([]int32, error) {
 
 	return ret, nil
 }
+
+func splitProcStat(content []byte) []string {
+	nameStart := bytes.IndexByte(content, '(')
+	nameEnd := bytes.LastIndexByte(content, ')')
+	restFields := strings.Fields(string(content[nameEnd+2:])) // +2 skip ') '
+	name := content[nameStart+1 : nameEnd]
+	pid := strings.TrimSpace(string(content[:nameStart]))
+	fields := make([]string, 3, len(restFields)+3)
+	fields[1] = string(pid)
+	fields[2] = string(name)
+	fields = append(fields, restFields...)
+	return fields
+}

v3/process/process_test.go

@@ -303,6 +303,48 @@ func Test_Process_Threads(t *testing.T) {
 	}
 }
 
+func Test_Process_splitProcStat(t *testing.T) {
+	expectedFieldsNum := 53
+	statLineContent := make([]string, expectedFieldsNum-1)
+	for i := 0; i < expectedFieldsNum-1; i++ {
+		statLineContent[i] = strconv.Itoa(i + 1)
+	}
+
+	cases := []string{
+		"ok",
+		"ok)",
+		"(ok",
+		"ok )",
+		"ok )(",
+		"ok )()",
+		"() ok )()",
+		"() ok (()",
+		" ) ok )",
+		"(ok) (ok)",
+	}
+
+	consideredFields := []int{4, 7, 10, 11, 12, 13, 14, 15, 18, 22, 42}
+
+	commandNameIndex := 2
+	for _, expectedName := range cases {
+		statLineContent[commandNameIndex-1] = "(" + expectedName + ")"
+		statLine := strings.Join(statLineContent, " ")
+		t.Run(fmt.Sprintf("name: %s", expectedName), func(t *testing.T) {
+			parsedStatLine := splitProcStat([]byte(statLine))
+			assert.Equal(t, expectedName, parsedStatLine[commandNameIndex])
+			for _, idx := range consideredFields {
+				idxByProcMan := idx + 1
+				expected := statLineContent[idx]
+				parsed := parsedStatLine[idxByProcMan]
+				assert.Equal(
+					t, expected, parsed,
+					"field %d (index from 1 as in man proc) must have index %s", idxByProcMan, expected,
+				)
+			}
+		})
+	}
+}
+
 func Test_Process_Name(t *testing.T) {
 	p := testGetProcess()