add version, help printing to main()

main.go

@@ -12,24 +12,26 @@ import (
 )
 
 var (
-	build   = ""
+	build   = "none"
 	version = "dev-build"
 
 	log    *logging.CTopLogger
 	cursor *GridCursor
-	cGrid  = compact.NewCompactGrid()
-	header = widgets.NewCTopHeader()
+	cGrid  *compact.CompactGrid
+	header *widgets.CTopHeader
 )
 
 func main() {
-	defer func() {
-		if r := recover(); r != nil {
-			ui.Clear()
-			fmt.Printf("panic: %s\n", r)
-			os.Exit(1)
-		}
-	}()
+	readArgs()
+	defer panicExit()
 
+	// init ui
+	if err := ui.Init(); err != nil {
+		panic(err)
+	}
+	defer ui.Close()
+
+	// init global config
 	config.Init()
 
 	// init logger
@@ -38,12 +40,10 @@ func main() {
 		logging.StartServer()
 	}
 
-	// init ui, grid
-	if err := ui.Init(); err != nil {
-		panic(err)
-	}
-	defer ui.Close()
+	// init grid, cursor, header
 	cursor = NewGridCursor()
+	cGrid = compact.NewCompactGrid()
+	header = widgets.NewCTopHeader()
 
 	for {
 		exit := Display()
@@ -54,3 +54,47 @@ func main() {
 		}
 	}
 }
+
+func readArgs() {
+	if len(os.Args) < 2 {
+		return
+	}
+	for _, arg := range os.Args[1:] {
+		switch arg {
+		case "-v", "version":
+			printVersion()
+			os.Exit(0)
+		case "-h", "help":
+			printHelp()
+			os.Exit(0)
+		default:
+			fmt.Printf("invalid option or argument: \"%s\"\n", arg)
+			os.Exit(1)
+		}
+	}
+}
+
+func panicExit() {
+	if r := recover(); r != nil {
+		ui.Clear()
+		fmt.Printf("panic: %s\n", r)
+		os.Exit(1)
+	}
+}
+
+var helpMsg = `cTop - container metric viewer
+
+usage: ctop [options]
+
+options:
+ -h display this help dialog
+ -v output version information and exit
+`
+
+func printHelp() {
+	fmt.Println(helpMsg)
+}
+
+func printVersion() {
+	fmt.Printf("cTop version %v, build %v\n", version, build)
+}