add filelock

cmd/update.go

@@ -18,6 +18,10 @@ type Failure struct {
 }
 
 func Update(cmd *cobra.Command, args []string) {
+	lock, err := lib.AcquireLock()
+	if err != nil {
+		log.Fatalf("%v, is ublue-upd already running?", err)
+	}
 	systemDriver, err := drv.GetSystemUpdateDriver()
 	if err != nil {
 		log.Fatalf("Failed to get system update driver")
@@ -171,4 +175,5 @@ func Update(cmd *cobra.Command, args []string) {
 		return
 	}
 	log.Printf("Updates Completed")
+	lib.ReleaseLock(lock)
 }

lib/filelock.go

@@ -1,11 +1,15 @@
 package lib
 
 import (
+	"fmt"
 	"io"
 	"os"
 	"syscall"
+	"time"
 )
 
+const fileLockPath string = "/run/ublue-upd.lock"
+
 func IsFileLocked(file *os.File) bool {
 	lock := syscall.Flock_t{
 		Type:   syscall.F_WRLCK,
@@ -17,3 +21,35 @@ func IsFileLocked(file *os.File) bool {
 	}
 	return lock.Type != syscall.F_UNLCK
 }
+
+func AcquireLock() (*os.File, error) {
+	file, err := os.OpenFile(fileLockPath, os.O_RDONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return nil, err
+	}
+
+	timeout := 5.0
+	startTime := time.Now()
+	var lockFile *os.File
+
+	for time.Since(startTime).Seconds() < timeout {
+		err = syscall.Flock(int(file.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
+		if err == nil {
+			lockFile = file
+			break
+		}
+
+		time.Sleep(1 * time.Second)
+	}
+
+	if lockFile == nil {
+		file.Close()
+		return nil, fmt.Errorf("Could not acquire lock at %s", fileLockPath)
+	}
+
+	return lockFile, nil
+}
+
+func ReleaseLock(file *os.File) error {
+	return syscall.Close(int(file.Fd()))
+}