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_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")
 }