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_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")
 }