Add usage info to gobetween

tools/go/gobetween/gobetween.go

@@ -11,6 +11,19 @@ import (
 	"strings"
 )
 
+func printUsage() {
+	fmt.Fprintf(os.Stderr, "Usage: %s [options] <range specification> [file]\n", os.Args[0])
+	fmt.Fprintln(os.Stderr, "Options:")
+	flag.PrintDefaults()
+	fmt.Fprintln(os.Stderr, "\nRange specification examples:")
+	fmt.Fprintln(os.Stderr, "10,20      Reads lines 10 to 20 from the input")
+	fmt.Fprintln(os.Stderr, "15:+5      Reads 5 lines starting from line 15")
+	fmt.Fprintln(os.Stderr, "3          Reads from line 3 to the end of the file")
+	fmt.Fprintln(os.Stderr, "+2         Reads the first 2 lines")
+	fmt.Fprintln(os.Stderr, "Please ensure you input valid range specifications and file paths.")
+	os.Exit(1)
+}
+
 func parseArgs(args []string) (int, int, string, error) {
 	var filename string
 	var start, length, end int
@@ -66,7 +79,7 @@ func parseArgs(args []string) (int, int, string, error) {
 				found = true
 			} else {
 				found = false
-				log.Fatal("No match found")
+				printUsage()
 			}
 		}
 	}
@@ -92,6 +105,11 @@ func main() {
 	flag.Parse()
 	args := flag.Args()
 
+	if len(args) < 1 {
+		printUsage()
+		os.Exit(1)
+	}
+
 	startIndex, endIndex, filename, err := parseArgs(args)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error parsing arguments: %v\n", err)