log: move log file to temp directory with fallback

main.go

@@ -161,7 +161,7 @@ func main() {
 	mem := flag.Uint64("mem", 512*1024*1024, "memory threshold in bytes")
 	interval := flag.Duration("interval", time.Minute, "scan interval")
 	dryRun := flag.Bool("dry-run", false, "log only, do not change priorities")
-	doLog := flag.Bool("log", true, "write log file next to executable")
+	doLog := flag.Bool("log", true, "write log file to temp directory")
 	flag.Parse()
 
 	if *interval < 10*time.Second {
@@ -170,8 +170,12 @@ func main() {
 
 	var logFile *os.File
 	if *doLog {
-		exePath, _ := os.Executable()
-		f, err := os.OpenFile(filepath.Join(filepath.Dir(exePath), "autopriority.log"),
+		logDir := os.TempDir()
+		if logDir == "" {
+			exePath, _ := os.Executable()
+			logDir = filepath.Dir(exePath)
+		}
+		f, err := os.OpenFile(filepath.Join(logDir, "autopriority.log"),
 			os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
 		if err == nil {
 			logFile = f