Add support for retrieving service status (#143)

* update command execution to support returing error codes, and stdout

add function to service interface to support returning service status

clean up places where strings were being converted to strings

* Spelling fix

* Simply service Status method

Add stopped detection to launchd
Switch to case statements
Return ErrNotInstalled in situations where we should

service.go

@@ -88,6 +88,16 @@ const (
 	optionLaunchdConfig = "LaunchdConfig"
 )
 
+// Status represents service status as an byte value
+type Status byte
+
+// Status of service represented as an byte
+const (
+	StatusUnknown Status = iota // Status is unable to be determined due to an error or it was not installed.
+	StatusRunning
+	StatusStopped
+)
+
 // Config provides the setup for a Service. The Name field is required.
 type Config struct {
 	Name        string   // Required name of the service. No spaces suggested.
@@ -132,10 +142,12 @@ var (
 )
 
 var (
-	// ErrNameFieldRequired is returned when Conifg.Name is empty.
+	// ErrNameFieldRequired is returned when Config.Name is empty.
 	ErrNameFieldRequired = errors.New("Config.Name field is required.")
 	// ErrNoServiceSystemDetected is returned when no system was detected.
 	ErrNoServiceSystemDetected = errors.New("No service system detected.")
+	// ErrNotInstalled is returned when the service is not installed
+	ErrNotInstalled = errors.New("the service is not installed")
 )
 
 // New creates a new service based on a service interface and configuration.
@@ -334,6 +346,9 @@ type Service interface {
 	// String displays the name of the service. The display name if present,
 	// otherwise the name.
 	String() string
+
+	// Status returns the current service status.
+	Status() (Status, error)
 }
 
 // ControlAction list valid string texts to use in Control.

service_darwin.go

@@ -11,6 +11,8 @@ import (
 	"os/signal"
 	"os/user"
 	"path/filepath"
+	"regexp"
+	"strings"
 	"syscall"
 	"text/template"
 	"time"
@@ -175,6 +177,32 @@ func (s *darwinLaunchdService) Uninstall() error {
 	return os.Remove(confPath)
 }
 
+func (s *darwinLaunchdService) Status() (Status, error) {
+	exitCode, out, err := runWithOutput("launchctl", "list", s.Name)
+	if exitCode == 0 && err != nil {
+		if !strings.Contains(err.Error(), "failed with stderr") {
+			return StatusUnknown, err
+		}
+	}
+
+	re := regexp.MustCompile(`"PID" = ([0-9]+);`)
+	matches := re.FindStringSubmatch(out)
+	if len(matches) == 2 {
+		return StatusRunning, nil
+	}
+
+	confPath, err := s.getServiceFilePath()
+	if err != nil {
+		return StatusUnknown, err
+	}
+
+	if _, err = os.Stat(confPath); err == nil {
+		return StatusStopped, nil
+	}
+
+	return StatusUnknown, ErrNotInstalled
+}
+
 func (s *darwinLaunchdService) Start() error {
 	confPath, err := s.getServiceFilePath()
 	if err != nil {

service_systemd_linux.go

@@ -8,10 +8,10 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"os/exec"
 	"os/signal"
 	"regexp"
 	"strconv"
+	"strings"
 	"syscall"
 	"text/template"
 )
@@ -57,13 +57,13 @@ func (s *systemd) configPath() (cp string, err error) {
 }
 
 func (s *systemd) getSystemdVersion() int64 {
-	out, err := exec.Command("/usr/bin/systemctl", "--version").Output()
+	_, out, err := runWithOutput("systemctl", "--version")
 	if err != nil {
 		return -1
 	}
 
 	re := regexp.MustCompile(`systemd ([0-9]+)`)
-	matches := re.FindStringSubmatch(string(out))
+	matches := re.FindStringSubmatch(out)
 	if len(matches) != 2 {
 		return -1
 	}
@@ -189,6 +189,24 @@ func (s *systemd) Run() (err error) {
 	return s.i.Stop(s)
 }
 
+func (s *systemd) Status() (Status, error) {
+	exitCode, out, err := runWithOutput("systemctl", "is-active", s.Name)
+	if exitCode == 0 && err != nil {
+		return StatusUnknown, err
+	}
+
+	switch {
+	case strings.HasPrefix(out, "active"):
+		return StatusRunning, nil
+	case strings.HasPrefix(out, "inactive"):
+		return StatusStopped, nil
+	case strings.HasPrefix(out, "failed"):
+		return StatusUnknown, errors.New("service in failed state")
+	default:
+		return StatusUnknown, ErrNotInstalled
+	}
+}
+
 func (s *systemd) Start() error {
 	return run("systemctl", "start", s.Name+".service")
 }

service_sysv_linux.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
+	"strings"
 	"syscall"
 	"text/template"
 	"time"
@@ -143,6 +144,22 @@ func (s *sysv) Run() (err error) {
 	return s.i.Stop(s)
 }
 
+func (s *sysv) Status() (Status, error) {
+	_, out, err := runWithOutput("service", s.Name, "status")
+	if err != nil {
+		return StatusUnknown, err
+	}
+
+	switch {
+	case strings.HasPrefix(out, "Running"):
+		return StatusRunning, nil
+	case strings.HasPrefix(out, "Stopped"):
+		return StatusStopped, nil
+	default:
+		return StatusUnknown, ErrNotInstalled
+	}
+}
+
 func (s *sysv) Start() error {
 	return run("service", s.Name, "start")
 }

service_unix.go

@@ -8,9 +8,11 @@ package service
 
 import (
 	"fmt"
+	"io"
 	"io/ioutil"
 	"log/syslog"
 	"os/exec"
+	"syscall"
 )
 
 func newSysLogger(name string, errs chan<- error) (Logger, error) {
@@ -53,20 +55,43 @@ func (s sysLogger) Infof(format string, a ...interface{}) error {
 }
 
 func run(command string, arguments ...string) error {
+	_, _, err := runCommand(command, false, arguments...)
+	return err
+}
+
+func runWithOutput(command string, arguments ...string) (int, string, error) {
+	return runCommand(command, true, arguments...)
+}
+
+func runCommand(command string, readStdout bool, arguments ...string) (int, string, error) {
 	cmd := exec.Command(command, arguments...)
 
+	var output string
+	var stdout io.ReadCloser
+	var err error
+
+	if readStdout {
+		// Connect pipe to read Stdout
+		stdout, err = cmd.StdoutPipe()
+
+		if err != nil {
+			// Failed to connect pipe
+			return 0, "", fmt.Errorf("%q failed to connect stdout pipe: %v", command, err)
+		}
+	}
+
 	// Connect pipe to read Stderr
 	stderr, err := cmd.StderrPipe()
 
 	if err != nil {
 		// Failed to connect pipe
-		return fmt.Errorf("%q failed to connect stderr pipe: %v", command, err)
+		return 0, "", fmt.Errorf("%q failed to connect stderr pipe: %v", command, err)
 	}
 
 	// Do not use cmd.Run()
 	if err := cmd.Start(); err != nil {
 		// Problem while copying stdin, stdout, or stderr
-		return fmt.Errorf("%q failed: %v", command, err)
+		return 0, "", fmt.Errorf("%q failed: %v", command, err)
 	}
 
 	// Zero exit status
@@ -75,14 +100,39 @@ func run(command string, arguments ...string) error {
 	if command == "launchctl" {
 		slurp, _ := ioutil.ReadAll(stderr)
 		if len(slurp) > 0 {
-			return fmt.Errorf("%q failed with stderr: %s", command, slurp)
+			return 0, "", fmt.Errorf("%q failed with stderr: %s", command, slurp)
+		}
+	}
+
+	if readStdout {
+		out, err := ioutil.ReadAll(stdout)
+		if err != nil {
+			return 0, "", fmt.Errorf("%q failed while attempting to read stdout: %v", command, err)
+		} else if len(out) > 0 {
+			output = string(out)
 		}
 	}
 
 	if err := cmd.Wait(); err != nil {
-		// Command didn't exit with a zero exit status.
-		return fmt.Errorf("%q failed: %v", command, err)
+		exitStatus, ok := isExitError(err)
+		if ok {
+			// Command didn't exit with a zero exit status.
+			return exitStatus, output, err
+		}
+
+		// An error occurred and there is no exit status.
+		return 0, output, fmt.Errorf("%q failed: %v", command, err)
 	}
 
-	return nil
+	return 0, output, nil
+}
+
+func isExitError(err error) (int, bool) {
+	if exiterr, ok := err.(*exec.ExitError); ok {
+		if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
+			return status.ExitStatus(), true
+		}
+	}
+
+	return 0, false
 }

service_upstart_linux.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"os/exec"
 	"os/signal"
 	"regexp"
 	"strings"
@@ -21,8 +20,8 @@ func isUpstart() bool {
 		return true
 	}
 	if _, err := os.Stat("/sbin/initctl"); err == nil {
-		if out, err := exec.Command("/sbin/initctl", "--version").Output(); err == nil {
-			if strings.Contains(string(out), "initctl (upstart") {
+		if _, out, err := runWithOutput("/sbin/initctl", "--version"); err == nil {
+			if strings.Contains(out, "initctl (upstart") {
 				return true
 			}
 		}
@@ -96,13 +95,13 @@ func (s *upstart) hasSetUIDStanza() bool {
 }
 
 func (s *upstart) getUpstartVersion() []int {
-	out, err := exec.Command("/sbin/initctl", "--version").Output()
+	_, out, err := runWithOutput("/sbin/initctl", "--version")
 	if err != nil {
 		return nil
 	}
 
 	re := regexp.MustCompile(`initctl \(upstart (\d+.\d+.\d+)\)`)
-	matches := re.FindStringSubmatch(string(out))
+	matches := re.FindStringSubmatch(out)
 	if len(matches) != 2 {
 		return nil
 	}
@@ -194,6 +193,22 @@ func (s *upstart) Run() (err error) {
 	return s.i.Stop(s)
 }
 
+func (s *upstart) Status() (Status, error) {
+	exitCode, out, err := runWithOutput("initctl", "status", s.Name)
+	if exitCode == 0 && err != nil {
+		return StatusUnknown, err
+	}
+
+	switch {
+	case strings.HasPrefix(out, fmt.Sprintf("%s start/running", s.Name)):
+		return StatusRunning, nil
+	case strings.HasPrefix(out, fmt.Sprintf("%s stop/waiting", s.Name)):
+		return StatusStopped, nil
+	default:
+		return StatusUnknown, ErrNotInstalled
+	}
+}
+
 func (s *upstart) Start() error {
 	return run("initctl", "start", s.Name)
 }

service_windows.go

@@ -275,6 +275,46 @@ func (ws *windowsService) Run() error {
 	return ws.i.Stop(ws)
 }
 
+func (ws *windowsService) Status() (Status, error) {
+	m, err := mgr.Connect()
+	if err != nil {
+		return StatusUnknown, err
+	}
+	defer m.Disconnect()
+
+	s, err := m.OpenService(ws.Name)
+	if err != nil {
+		if err.Error() == "The specified service does not exist as an installed service." {
+			return StatusUnknown, ErrNotInstalled
+		}
+		return StatusUnknown, err
+	}
+
+	status, err := s.Query()
+	if err != nil {
+		return StatusUnknown, err
+	}
+
+	switch status.State {
+	case svc.StartPending:
+		fallthrough
+	case svc.Running:
+		return StatusRunning, nil
+	case svc.PausePending:
+		fallthrough
+	case svc.Paused:
+		fallthrough
+	case svc.ContinuePending:
+		fallthrough
+	case svc.StopPending:
+		fallthrough
+	case svc.Stopped:
+		return StatusStopped, nil
+	default:
+		return StatusUnknown, fmt.Errorf("unknown status %s", status)
+	}
+}
+
 func (ws *windowsService) Start() error {
 	m, err := mgr.Connect()
 	if err != nil {