diff --git a/a2/disasm.go b/a2/disasm.go
index aa44645..f05d841 100644
--- a/a2/disasm.go
+++ b/a2/disasm.go
@@ -1,8 +1,8 @@
 package main
 
 import (
+	"fmt"
 	"io/ioutil"
-	"log"
 	"os"
 
 	"github.com/gonuts/commander"
@@ -24,23 +24,24 @@ func init() {
 	cmdDisasm.Flag.UintVar(&disasmAddress, "a", 0, "The starting memory address.")
 }
 
-func runDisasm(cmd *commander.Command, args []string) {
+func runDisasm(cmd *commander.Command, args []string) error {
 	if len(args) != 1 {
 		cmd.Usage()
-		return
+		return nil
 	}
 
 	bytes, err := ioutil.ReadFile(args[0])
 	if err != nil {
-		log.Fatal(err)
+		return nil
 	}
 	if len(bytes) > 0x10000 {
-		log.Fatalf("File %s is %04X bytes long, which is more than $10000.", args[0], len(bytes))
+		return fmt.Errorf("File %s is %04X bytes long, which is more than $10000.", args[0], len(bytes))
 	}
 	if int(disasmAddress)+len(bytes) > 0x10000 {
-		log.Fatalf("Starting address ($%04X) + file length ($%04X) = $%X, which is > $10000",
+		return fmt.Errorf("Starting address ($%04X) + file length ($%04X) = $%X, which is > $10000",
 			disasmAddress, len(bytes), int(disasmAddress)+len(bytes))
 	}
 
 	asm.DisasmBlock(bytes, uint16(disasmAddress), os.Stdout)
+	return nil
 }
diff --git a/a2/disk_convert.go b/a2/disk_convert.go
index 397391a..8d5d276 100644
--- a/a2/disk_convert.go
+++ b/a2/disk_convert.go
@@ -1,7 +1,7 @@
 package main
 
 import (
-	"log"
+	"fmt"
 
 	"github.com/gonuts/commander"
 	"github.com/zellyn/goapple2/disk"
@@ -22,19 +22,21 @@ func init() {
 	cmdDiskConvert.Flag.UintVar(&diskVolume, "v", 0, "The volume of the disk, or 0 for default.")
 }
 
-func runDiskConvert(cmd *commander.Command, args []string) {
+func runDiskConvert(cmd *commander.Command, args []string) error {
 	if len(args) != 2 {
 		cmd.Usage()
-		return
+		return nil
 	}
 	if diskVolume > 254 {
-		log.Fatalf("disk volume must be 0-254, got %d", diskVolume)
+		return fmt.Errorf("disk volume must be 0-254, got %d", diskVolume)
 	}
 	nyb, err := disk.DiskFromFile(args[0], byte(diskVolume))
 	if err != nil {
-		log.Fatal(err)
+		return err
 	}
 	if err = disk.DiskToFile(args[1], nyb); err != nil {
-		log.Fatal(err)
+		return err
 	}
+
+	return err
 }
diff --git a/a2/main.go b/a2/main.go
index 4bd9258..f727177 100644
--- a/a2/main.go
+++ b/a2/main.go
@@ -8,25 +8,21 @@ import (
 	"github.com/gonuts/flag"
 )
 
-var a2cmd *commander.Commander
+var a2cmd *commander.Command
 
 func init() {
-	a2cmd = &commander.Commander{
-		Name: os.Args[0],
-		Commands: []*commander.Command{
+	a2cmd = &commander.Command{
+		UsageLine: "a2",
+		Subcommands: []*commander.Command{
 			cmdDisasm,
 			cmdDiskConvert,
 		},
-		Flag: flag.NewFlagSet("a2", flag.ExitOnError),
+		Flag: *flag.NewFlagSet("a2", flag.ExitOnError),
 	}
 }
 
 func main() {
-	if err := a2cmd.Flag.Parse(os.Args[1:]); err != nil {
-		log.Fatal(err)
-	}
-	args := a2cmd.Flag.Args()
-	if err := a2cmd.Run(args); err != nil {
+	if err := a2cmd.Dispatch(os.Args[1:]); err != nil {
 		log.Fatal(err)
 	}
 }