Merge pull request #7 from DominicBreuker/fix-read-syscall

Fix errno 22 errors

Makefile

@@ -14,14 +14,10 @@ test:
 	docker build -f $(TEST_DOCKERFILE) -t $(TEST_IMAGE) . 
 	docker run -it --rm $(TEST_IMAGE)
 
-# Build Docker image for development
-# pspy has to run on Linux - use this if you develop on another OS
-dev-build:
-	docker build -f $(DEV_DOCKERFILE) -t $(DEV_IMAGE) .
-
 # Drops you into a shell in the development container and mounts the source code
 # You can edit to source on your host, then run go commans (e.g., `go test ./...`) inside the container
 dev:
+	sh -c "if ! docker image ls | grep '$(DEV_IMAGE)' | cut -d ':' -f1; then echo 'building dev image'; docker build -f $(DEV_DOCKERFILE) -t $(DEV_IMAGE) .; fi"
 	docker run -it \
 		       --rm \
 			   -v $(PROJECT_DIR):/go/src/github.com/dominicbreuker/pspy \
@@ -37,14 +33,13 @@ example:
 	docker run -it --rm $(EXAMPLE_IMAGE)
 
 
-build-build-image:
-	docker build -f $(BUILD_DOCKERFILE) -t $(BUILD_IMAGE) .
-
 # Build different binaries
 # builds binaries for both 32bit and 64bit systems
 # builds one set of static binaries that should work on any system without dependencies, but are huge
 # builds another set of binaries that are as small as possible, but may not work 
 build:
+	sh -c "if ! docker image ls | grep '$(BUILD_IMAGE)' | cut -d ':' -f1; then echo 'building build image'; docker build -f $(BUILD_DOCKERFILE) -t $(BUILD_IMAGE) .; fi"
+
 	mkdir -p $(PROJECT_DIR)/bin
 	docker run -it \
 		       --rm \

README.md

@@ -17,17 +17,23 @@ Inotify watchers placed on selected parts of the file system trigger these scans
 
 ## Getting started
 
-Get the tool onto the Linux machine you want to inspect.
-First get the binaries.
+### Download
+
+Get the tool onto the Linux machine you want to inspect.
+First get the binaries. Download the released binaries here:
+- 32 bit big, static version: `pspy32` [download](https://github.com/DominicBreuker/pspy/releases/download/v1.0.0/pspy32)
+- 64 bit big, static version: `pspy64` [download](https://github.com/DominicBreuker/pspy/releases/download/v1.0.0/pspy64)
+- 32 bit small version: `pspy32s` [download](https://github.com/DominicBreuker/pspy/releases/download/v1.0.0/pspy32s)
+- 64 bit small version: `pspy64s` [download](https://github.com/DominicBreuker/pspy/releases/download/v1.0.0/pspy64s)
 
-You can build them yourself by running `make build-build-image` to build a docker image used in `make build` to build four binaries:
-- 32 bit big, static version: `pspy32`
-- 64 bit big, static version: `pspy64`
-- 32 bit small version: `pspy32s`
-- 64 bit small version: `pspy64s`
 The statically compiled files should work on any Linux system but are quite huge (~4MB).
 If size is an issue, try the smaller versions which depend on libc and are compressed with UPX (<1MB).
 
+### Build
+
+Either use Go installed on your system or run the Docker-based build process which ran to create the release.
+For the latter, ensure Docker is installed, and then run `make build-build-image` to build a Docker image, followed by `make build` to build the binaries with it.
+
 You can run `pspy --help` to learn about the flags and their meaning.
 The summary is as follows:
 - -p: enables printing commands to stdout (enabled by default)

cmd/root.go

@@ -58,6 +58,7 @@ var defaultRDirs = []string{
 var defaultDirs = []string{}
 var triggerInterval int
 var colored bool
+var debug bool
 
 func init() {
 	rootCmd.PersistentFlags().BoolVarP(&logPS, "procevents", "p", true, "print new processes to stdout")
@@ -66,12 +67,13 @@ func init() {
 	rootCmd.PersistentFlags().StringArrayVarP(&dirs, "dirs", "d", defaultDirs, "watch these dirs")
 	rootCmd.PersistentFlags().IntVarP(&triggerInterval, "interval", "i", 100, "scan every 'interval' milliseconds for new processes")
 	rootCmd.PersistentFlags().BoolVarP(&colored, "color", "c", true, "color the printed events")
+	rootCmd.PersistentFlags().BoolVarP(&debug, "debug", "", false, "print detailed error messages")
 
 	log.SetOutput(os.Stdout)
 }
 
 func root(cmd *cobra.Command, args []string) {
-	logger := logging.NewLogger()
+	logger := logging.NewLogger(debug)
 
 	cfg := &config.Config{
 		RDirs:        rDirs,

docker/Dockerfile.build

@@ -1,3 +1,3 @@
-FROM golang:1.10-stretch
+FROM golang:1.12-stretch
 
 RUN apt-get update && apt-get install -y upx && rm -rf /var/lib/apt/lists/*

docker/Dockerfile.development

@@ -1,4 +1,4 @@
-FROM golang:1.10-stretch
+FROM golang:1.12-stretch
 
 RUN apt-get update && apt-get -y install cron python3 sudo procps
 

docker/Dockerfile.testing

@@ -1,4 +1,4 @@
-FROM golang:1.10-stretch
+FROM golang:1.12-stretch
 
 RUN apt-get update && apt-get -y install cron python3 sudo procps
 

internal/fswatcher/inotify/inotify.go

@@ -17,7 +17,8 @@ const maximumWatchersFile = "/proc/sys/fs/inotify/max_user_watches"
 // set to -1 if the number cannot be determined
 var MaxWatchers int = -1
 
-const EventSize int = unix.SizeofInotifyEvent
+// sizeof(struct inotify_event) + NAME_MAX + 1
+const EventSize int = unix.SizeofInotifyEvent + 255 + 1
 
 func init() {
 	mw, err := getMaxWatchers()
@@ -71,7 +72,7 @@ func (i *Inotify) Watch(dir string) error {
 
 func (i *Inotify) Read(buf []byte) (int, error) {
 	n, errno := unix.Read(i.FD, buf)
-	if n < 0 {
+	if n < 1 {
 		return n, fmt.Errorf("reading from inotify fd %d: errno: %d", i.FD, errno)
 	}
 	return n, nil

internal/logging/logging.go

@@ -2,27 +2,35 @@ package logging
 
 import (
 	"fmt"
+	"hash/fnv"
 	"log"
 	"os"
+	"strconv"
 )
 
 const (
 	ColorNone = iota
 	ColorRed
 	ColorGreen
+	ColorYellow
+	ColorBlue
+	ColorPurple
+	ColorTeal
 )
 
 type Logger struct {
 	infoLogger  *log.Logger
 	errorLogger *log.Logger
 	eventLogger *log.Logger
+	debug       bool
 }
 
-func NewLogger() *Logger {
+func NewLogger(debug bool) *Logger {
 	return &Logger{
 		infoLogger:  log.New(os.Stdout, "", 0),
 		errorLogger: log.New(os.Stderr, "", 0),
 		eventLogger: log.New(os.Stdout, "", log.Ldate|log.Ltime),
+		debug:       debug,
 	}
 }
 
@@ -32,21 +40,24 @@ func (l *Logger) Infof(format string, v ...interface{}) {
 }
 
 // Errorf writes an error message to stderr
-func (l *Logger) Errorf(format string, v ...interface{}) {
+func (l *Logger) Errorf(debug bool, format string, v ...interface{}) {
+	if l.debug == debug {
 		l.errorLogger.Printf(format, v...)
 	}
+}
 
 // Eventf writes an event with timestamp to stdout
 func (l *Logger) Eventf(color int, format string, v ...interface{}) {
 	msg := fmt.Sprintf(format, v...)
-
-	switch color {
-	case ColorRed:
-		msg = fmt.Sprintf("\x1b[31;1m%s\x1b[0m", msg)
-	case ColorGreen:
-		msg = fmt.Sprintf("\x1b[32;1m%s\x1b[0m", msg)
-	default:
+	if color != ColorNone {
+		msg = fmt.Sprintf("\x1b[%d;1m%s\x1b[0m", 30+color, msg)
 	}
 
 	l.eventLogger.Printf("%s", msg)
 }
+
+func GetColorByUID(uid int) int {
+	h := fnv.New32a()
+	h.Write([]byte(strconv.Itoa(uid)))
+	return (int(h.Sum32()) % (ColorTeal)) + 1
+}

internal/logging/logging_test.go

@@ -13,7 +13,7 @@ const ansiPattern = "[\u001B\u009B][[\\]()#;?]*(?:(?:(?:[a-zA-Z\\d]*(?:;[a-zA-Z\
 
 var ansiMatcher = regexp.MustCompile(ansiPattern)
 
-var l = NewLogger()
+var l = NewLogger(true)
 
 var logTests = []struct {
 	logger      *log.Logger
@@ -23,8 +23,8 @@ var logTests = []struct {
 }{
 	{l.infoLogger, func() { l.Infof("Info message no. %d", 1) }, "Info message no. 1\n", nil},
 	{l.infoLogger, func() { l.Infof("Info message no. %d with a string %s\n", 2, "appended to it") }, "Info message no. 2 with a string appended to it\n", nil},
-	{l.errorLogger, func() { l.Errorf("Error message") }, "Error message\n", nil},
-	{l.errorLogger, func() { l.Errorf("Error message\n") }, "Error message\n", nil},
+	{l.errorLogger, func() { l.Errorf(true, "Error message") }, "Error message\n", nil},
+	{l.errorLogger, func() { l.Errorf(true, "Error message\n") }, "Error message\n", nil},
 	{l.eventLogger, func() { l.Eventf(ColorNone, "Event message") }, dateFormatPattern + " Event message\n", nil},
 	{l.eventLogger, func() { l.Eventf(ColorRed, "Event message") }, dateFormatPattern + " Event message\n", [][]byte{[]byte("\x1b[31;1m"), []byte("\x1b[0m")}},
 	{l.eventLogger, func() { l.Eventf(ColorGreen, "Event message") }, dateFormatPattern + " Event message\n", [][]byte{[]byte("\x1b[32;1m"), []byte("\x1b[0m")}},
@@ -33,6 +33,7 @@ var logTests = []struct {
 func TestLogging(t *testing.T) {
 	for i, tt := range logTests {
 		actual := captureOutput(tt.logger, tt.test)
+		log.Printf("OUT: %s", actual)
 
 		// check colors and remove afterwards
 		colors := ansiMatcher.FindAll(actual, 2)
@@ -55,3 +56,46 @@ func captureOutput(logger *log.Logger, f func()) []byte {
 	f()
 	return buf.Bytes()
 }
+
+func TestGetColorByUID(t *testing.T) {
+	tests := []struct {
+		uid   int
+		color int
+	}{
+		{uid: 0, color: 4},
+		{uid: 1, color: 5},
+		{uid: 2, color: 2},
+		{uid: 3, color: 3},
+		{uid: 99999999999, color: 5},
+	}
+
+	for _, tt := range tests {
+		color := GetColorByUID(tt.uid)
+		if color != tt.color {
+			t.Errorf("GetColorByUID(%d)=%d but want %d", tt.uid, color, tt.color)
+		}
+	}
+
+	minColor := 9999999
+	maxColor := -9999999
+	for i := 0; i < 1000; i++ {
+		color := GetColorByUID(i)
+		if color < 1 || color > ColorTeal {
+			t.Fatalf("GetColorByUID(%d)=%d but this is out of range [%d, %d]", i, color, ColorRed, ColorTeal)
+		}
+
+		if color < minColor {
+			minColor = color
+		}
+		if color > maxColor {
+			maxColor = color
+		}
+	}
+
+	if minColor != 1 {
+		t.Errorf("GetColorByUID returned minimum color %d, not %d, on 1000 trials, which is extremely unlikely", minColor, 1)
+	}
+	if maxColor != ColorTeal {
+		t.Errorf("GetColorByUID returned maximum color %d, not %d, on 1000 trials, which is extremely unlikely", maxColor, ColorTeal)
+	}
+}

internal/pspy/pspy.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/dominicbreuker/pspy/internal/config"
 	"github.com/dominicbreuker/pspy/internal/logging"
+	"github.com/dominicbreuker/pspy/internal/psscanner"
 )
 
 type Bindings struct {
@@ -16,7 +17,7 @@ type Bindings struct {
 
 type Logger interface {
 	Infof(format string, v ...interface{})
-	Errorf(format string, v ...interface{})
+	Errorf(debug bool, format string, v ...interface{})
 	Eventf(color int, format string, v ...interface{})
 }
 
@@ -26,13 +27,13 @@ type FSWatcher interface {
 }
 
 type PSScanner interface {
-	Run(triggerCh chan struct{}) (chan string, chan error)
+	Run(triggerCh chan struct{}) (chan psscanner.PSEvent, chan error)
 }
 
 type chans struct {
 	sigCh     chan os.Signal
 	fsEventCh chan string
-	psEventCh chan string
+	psEventCh chan psscanner.PSEvent
 }
 
 func Start(cfg *config.Config, b *Bindings, sigCh chan os.Signal) chan struct{} {
@@ -56,7 +57,7 @@ func Start(cfg *config.Config, b *Bindings, sigCh chan os.Signal) chan struct{}
 
 func printOutput(cfg *config.Config, b *Bindings, chans *chans) chan struct{} {
 	exit := make(chan struct{})
-	fsEventColor, psEventColor := getColors(cfg.Colored)
+	// fsEventColor, psEventColor := getColors(cfg.Colored)
 
 	go func() {
 		for {
@@ -66,11 +67,15 @@ func printOutput(cfg *config.Config, b *Bindings, chans *chans) chan struct{} {
 				exit <- struct{}{}
 			case fe := <-chans.fsEventCh:
 				if cfg.LogFS {
-					b.Logger.Eventf(fsEventColor, "FS: %+v", fe)
+					b.Logger.Eventf(logging.ColorNone, "FS: %+v", fe)
 				}
 			case pe := <-chans.psEventCh:
 				if cfg.LogPS {
-					b.Logger.Eventf(psEventColor, "CMD: %+v", pe)
+					color := logging.ColorNone
+					if cfg.Colored {
+						color = logging.GetColorByUID(pe.UID)
+					}
+					b.Logger.Eventf(color, "CMD: %+v", pe)
 				}
 			}
 		}
@@ -78,17 +83,6 @@ func printOutput(cfg *config.Config, b *Bindings, chans *chans) chan struct{} {
 	return exit
 }
 
-func getColors(colored bool) (fsEventColor int, psEventColor int) {
-	if colored {
-		fsEventColor = logging.ColorGreen
-		psEventColor = logging.ColorRed
-	} else {
-		fsEventColor = logging.ColorNone
-		psEventColor = logging.ColorNone
-	}
-	return
-}
-
 func initFSW(fsw FSWatcher, rdirs, dirs []string, logger Logger) {
 	errCh, doneCh := fsw.Init(rdirs, dirs)
 	for {
@@ -96,7 +90,7 @@ func initFSW(fsw FSWatcher, rdirs, dirs []string, logger Logger) {
 		case <-doneCh:
 			return
 		case err := <-errCh:
-			logger.Errorf("initializing fs watcher: %v", err)
+			logger.Errorf(true, "initializing fs watcher: %v", err)
 		}
 	}
 }
@@ -112,7 +106,7 @@ func startFSW(fsw FSWatcher, logger Logger, drainFor time.Duration) (triggerCh c
 	return triggerCh, fsEventCh
 }
 
-func startPSS(pss PSScanner, logger Logger, triggerCh chan struct{}) (psEventCh chan string) {
+func startPSS(pss PSScanner, logger Logger, triggerCh chan struct{}) (psEventCh chan psscanner.PSEvent) {
 	psEventCh, errCh := pss.Run(triggerCh)
 	go logErrors(errCh, logger)
 	return psEventCh
@@ -130,7 +124,7 @@ func triggerEvery(d time.Duration, triggerCh chan struct{}) {
 func logErrors(errCh chan error, logger Logger) {
 	for {
 		err := <-errCh
-		logger.Errorf("ERROR: %v", err)
+		logger.Errorf(true, "ERROR: %v", err)
 	}
 }
 

internal/pspy/pspy_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/dominicbreuker/pspy/internal/config"
 	"github.com/dominicbreuker/pspy/internal/logging"
+	"github.com/dominicbreuker/pspy/internal/psscanner"
 )
 
 func TestInitFSW(t *testing.T) {
@@ -67,24 +68,6 @@ func TestStartPSS(t *testing.T) {
 	expectMessage(t, l.Error, "ERROR: error during refresh")
 }
 
-func TestGetColors(t *testing.T) {
-	tests := []struct {
-		colored      bool
-		fsEventColor int
-		psEventColor int
-	}{
-		{colored: true, fsEventColor: logging.ColorGreen, psEventColor: logging.ColorRed},
-		{colored: false, fsEventColor: logging.ColorNone, psEventColor: logging.ColorNone},
-	}
-
-	for _, tt := range tests {
-		c1, c2 := getColors(tt.colored)
-		if c1 != tt.fsEventColor || c2 != tt.psEventColor {
-			t.Errorf("Got wrong colors when colored=%t: expected %d, %d but got %d, %d", tt.colored, tt.fsEventColor, tt.psEventColor, c1, c2)
-		}
-	}
-}
-
 func TestStart(t *testing.T) {
 	drainFor := 10 * time.Millisecond
 	triggerEvery := 999 * time.Second
@@ -112,7 +95,7 @@ func TestStart(t *testing.T) {
 		close(fsw.initDoneCh)
 		<-time.After(2 * drainFor)
 		fsw.runTriggerCh <- struct{}{}
-		pss.runEventCh <- "pss event"
+		pss.runEventCh <- psscanner.PSEvent{UID: 1000, PID: 12345, CMD: "pss event"}
 		pss.runErrCh <- errors.New("pss error")
 		fsw.runEventCh <- "fsw event"
 		fsw.runErrCh <- errors.New("fsw error")
@@ -125,9 +108,9 @@ func TestStart(t *testing.T) {
 	<-time.After(2 * drainFor)
 	expectMessage(t, l.Info, "done")
 	expectTrigger(t, pss.runTriggerCh) // pss receives triggers from fsw
-	expectMessage(t, l.Event, fmt.Sprintf("%d CMD: pss event", logging.ColorRed))
+	expectMessage(t, l.Event, fmt.Sprintf("%d CMD: UID=1000 PID=12345  | pss event", logging.ColorPurple))
 	expectMessage(t, l.Error, "ERROR: pss error")
-	expectMessage(t, l.Event, fmt.Sprintf("%d FS: fsw event", logging.ColorGreen))
+	expectMessage(t, l.Event, fmt.Sprintf("%d FS: fsw event", logging.ColorNone))
 	expectMessage(t, l.Error, "ERROR: fsw error")
 	expectMessage(t, l.Info, "Exiting program... (interrupt)")
 
@@ -190,6 +173,7 @@ type mockLogger struct {
 	Info  chan string
 	Error chan string
 	Event chan string
+	Debug bool
 }
 
 func newMockLogger() *mockLogger {
@@ -197,6 +181,7 @@ func newMockLogger() *mockLogger {
 		Info:  make(chan string, 10),
 		Error: make(chan string, 10),
 		Event: make(chan string, 10),
+		Debug: true,
 	}
 }
 
@@ -204,9 +189,11 @@ func (l *mockLogger) Infof(format string, v ...interface{}) {
 	l.Info <- fmt.Sprintf(format, v...)
 }
 
-func (l *mockLogger) Errorf(format string, v ...interface{}) {
+func (l *mockLogger) Errorf(debug bool, format string, v ...interface{}) {
+	if l.Debug == debug {
 		l.Error <- fmt.Sprintf(format, v...)
 	}
+}
 
 func (l *mockLogger) Eventf(color int, format string, v ...interface{}) {
 	m := fmt.Sprintf(format, v...)
@@ -251,7 +238,7 @@ func (fsw *mockFSWatcher) Run() (chan struct{}, chan string, chan error) {
 
 type mockPSScanner struct {
 	runTriggerCh chan struct{}
-	runEventCh   chan string
+	runEventCh   chan psscanner.PSEvent
 	runErrCh     chan error
 	numRefreshes int
 }
@@ -260,9 +247,9 @@ func newMockPSScanner() *mockPSScanner {
 	return &mockPSScanner{}
 }
 
-func (pss *mockPSScanner) Run(triggerCh chan struct{}) (chan string, chan error) {
+func (pss *mockPSScanner) Run(triggerCh chan struct{}) (chan psscanner.PSEvent, chan error) {
 	pss.runTriggerCh = triggerCh
-	pss.runEventCh = make(chan string)
+	pss.runEventCh = make(chan psscanner.PSEvent)
 	pss.runErrCh = make(chan error)
 
 	go func() {

internal/psscanner/proclist.go

@@ -25,7 +25,7 @@ var cmdLineReader = func(pid int) ([]byte, error) {
 
 type procList map[int]string
 
-func (pl procList) refresh(eventCh chan string) error {
+func (pl procList) refresh(eventCh chan PSEvent) error {
 	pids, err := getPIDs()
 	if err != nil {
 		return err
@@ -74,16 +74,16 @@ func file2Pid(f os.FileInfo) (int, error) {
 	return pid, nil
 }
 
-func (pl procList) addPid(pid int, eventCh chan string) {
+func (pl procList) addPid(pid int, eventCh chan PSEvent) {
 	cmd, err := getCmd(pid)
 	if err != nil {
 		cmd = "???" // process probably terminated
 	}
 	uid, err := getUID(pid)
 	if err != nil {
-		uid = "???"
+		uid = -1
 	}
-	eventCh <- fmt.Sprintf("UID=%-4s PID=%-6d | %s", uid, pid, cmd)
+	eventCh <- PSEvent{UID: uid, PID: pid, CMD: cmd}
 	pl[pid] = cmd
 }
 
@@ -100,18 +100,26 @@ func getCmd(pid int) (string, error) {
 	return string(cmd), nil
 }
 
-func getUID(pid int) (string, error) {
+func getUID(pid int) (int, error) {
 	stat, err := procStatusReader(pid)
 	if err != nil {
-		return "", err
+		return -1, err
 	}
+
 	lines := strings.Split(string(stat), "\n")
 	if len(lines) < 9 {
-		return "", fmt.Errorf("no uid information")
+		return -1, fmt.Errorf("no uid information")
 	}
+
 	uidL := strings.Split(lines[8], "\t")
 	if len(uidL) < 2 {
-		return "", fmt.Errorf("uid line read incomplete")
+		return -1, fmt.Errorf("uid line read incomplete")
 	}
-	return uidL[1], nil
+
+	uid, err := strconv.Atoi(uidL[1])
+	if err != nil {
+		return -1, fmt.Errorf("converting %s to int: %v", uidL[1], err)
+	}
+
+	return uid, nil
 }

internal/psscanner/proclist_test.go

@@ -136,14 +136,14 @@ func TestGetUID(t *testing.T) {
 		pid     int
 		stat    []byte
 		statErr error
-		uid     string
+		uid     int
 		err     string
 	}{
-		{pid: 7, stat: completeStatus, statErr: nil, uid: "0", err: ""},                                         // can read normal stat
-		{pid: 7, stat: uidLineBroken, statErr: nil, uid: "", err: "uid line read incomplete"},                   // errors on incomplete Uid line
-		{pid: 7, stat: notEnoughLines, statErr: nil, uid: "", err: "no uid information"},                        // errors for insufficient lines
-		{pid: 7, stat: []byte(""), statErr: nil, uid: "", err: "no uid information"},                            // errors for insufficient lines
-		{pid: 7, stat: []byte(""), statErr: errors.New("file-system-error"), uid: "", err: "file-system-error"}, // returns file system errors
+		{pid: 7, stat: completeStatus, statErr: nil, uid: 0, err: ""},                                           // can read normal stat
+		{pid: 7, stat: uidLineBroken, statErr: nil, uid: -1, err: "uid line read incomplete"},                   // errors on incomplete Uid line
+		{pid: 7, stat: notEnoughLines, statErr: nil, uid: -1, err: "no uid information"},                        // errors for insufficient lines
+		{pid: 7, stat: []byte(""), statErr: nil, uid: -1, err: "no uid information"},                            // errors for insufficient lines
+		{pid: 7, stat: []byte(""), statErr: errors.New("file-system-error"), uid: -1, err: "file-system-error"}, // returns file system errors
 	}
 
 	for _, tt := range tests {
@@ -151,7 +151,7 @@ func TestGetUID(t *testing.T) {
 		uid, err := getUID(tt.pid)
 		if uid != tt.uid {
 			fmt.Printf("STAT: %s", tt.stat)
-			t.Errorf("Wrong uid returned: got %s but want %s", uid, tt.uid)
+			t.Errorf("Wrong uid returned: got %d but want %d", uid, tt.uid)
 		}
 		if (err != nil || tt.err != "") && fmt.Sprintf("%v", err) != tt.err {
 			t.Errorf("Wrong error returned: got %v but want %s", err, tt.err)
@@ -174,18 +174,18 @@ func mockProcStatusReader(stat []byte, err error) (restore func()) {
 
 func TestRefresh(t *testing.T) {
 	tests := []struct {
-		eventCh   chan string
+		eventCh   chan PSEvent
 		pl        procList
 		newPids   []int
 		pidsAfter []int
 		events    []string
 	}{
-		{eventCh: make(chan string), pl: procList{}, newPids: []int{1, 2, 3}, pidsAfter: []int{3, 2, 1}, events: []string{
+		{eventCh: make(chan PSEvent), pl: procList{}, newPids: []int{1, 2, 3}, pidsAfter: []int{3, 2, 1}, events: []string{
 			"UID=???  PID=3      | the-command",
 			"UID=???  PID=2      | the-command",
 			"UID=???  PID=1      | the-command",
 		}},
-		{eventCh: make(chan string), pl: procList{1: "pid-found-before"}, newPids: []int{1, 2, 3}, pidsAfter: []int{1, 3, 2}, events: []string{
+		{eventCh: make(chan PSEvent), pl: procList{1: "pid-found-before"}, newPids: []int{1, 2, 3}, pidsAfter: []int{1, 3, 2}, events: []string{
 			"UID=???  PID=3      | the-command",
 			"UID=???  PID=2      | the-command",
 		}}, // no events emitted for PIDs already known
@@ -200,7 +200,7 @@ func TestRefresh(t *testing.T) {
 		done := make(chan struct{})
 		go func() {
 			for e := range tt.eventCh {
-				events = append(events, e)
+				events = append(events, e.String())
 			}
 			done <- struct{}{}
 		}()

internal/psscanner/psscanner.go

@@ -1,13 +1,33 @@
 package psscanner
 
+import (
+	"fmt"
+	"strconv"
+)
+
 type PSScanner struct{}
 
+type PSEvent struct {
+	UID int
+	PID int
+	CMD string
+}
+
+func (evt PSEvent) String() string {
+	uid := strconv.Itoa(evt.UID)
+	if evt.UID == -1 {
+		uid = "???"
+	}
+
+	return fmt.Sprintf("UID=%-4s PID=%-6d | %s", uid, evt.PID, evt.CMD)
+}
+
 func NewPSScanner() *PSScanner {
 	return &PSScanner{}
 }
 
-func (p *PSScanner) Run(triggerCh chan struct{}) (chan string, chan error) {
-	eventCh := make(chan string, 100)
+func (p *PSScanner) Run(triggerCh chan struct{}) (chan PSEvent, chan error) {
+	eventCh := make(chan PSEvent, 100)
 	errCh := make(chan error)
 	pl := make(procList)
 

internal/psscanner/psscanner_test.go

@@ -48,7 +48,7 @@ func TestRun(t *testing.T) {
 			case <-time.After(timeout):
 				t.Errorf("did not receive event in time")
 			case e := <-eventCh:
-				if e != tt.events[i] {
+				if e.String() != tt.events[i] {
 					t.Errorf("Wrong event received: got '%s' but wanted '%s'", e, tt.events[i])
 				}
 			case err := <-errCh: