Use subcommands instead of flags

README.md

@@ -50,7 +50,7 @@ The debugger can be launched in three ways:
 * Compile, run, and attach in one step:
 
 	```
-	$ dlv -run
+	$ dlv run
 	```
 
 * Provide the name of the program you want to debug, and the debugger will launch it for you.
@@ -62,7 +62,7 @@ The debugger can be launched in three ways:
 * Provide the pid of a currently running process, and the debugger will attach and begin the session.
 
 	```
-	$ sudo dlv -pid 44839
+	$ sudo dlv attach 44839
 	```
 
 ### Breakpoints

client/cli/cli.go

@@ -7,6 +7,7 @@ import (
 	"os/exec"
 	"os/signal"
 	"strings"
+	"strconv"
 
 	sys "golang.org/x/sys/unix"
 
@@ -18,7 +19,7 @@ import (
 
 const historyFile string = ".dbg_history"
 
-func Run(run bool, pid int, args []string) {
+func Run(args []string) {
 	var (
 		dbp  *proctl.DebuggedProcess
 		err  error
@@ -26,8 +27,8 @@ func Run(run bool, pid int, args []string) {
 	)
 	defer line.Close()
 
-	switch {
-	case run:
+	switch args[0] {
+	case "run":
 		const debugname = "debug"
 		cmd := exec.Command("go", "build", "-o", debugname, "-gcflags", "-N -l")
 		err := cmd.Run()
@@ -40,7 +41,11 @@ func Run(run bool, pid int, args []string) {
 		if err != nil {
 			die(1, "Could not launch program:", err)
 		}
-	case pid != 0:
+	case "attach":
+		pid, err := strconv.Atoi(args[1])
+		if err != nil {
+			die(1, "Invalid pid", args[1])
+		}
 		dbp, err = proctl.Attach(pid)
 		if err != nil {
 			die(1, "Could not attach to process:", err)

cmd/dlv/main.go

@@ -11,6 +11,20 @@ import (
 
 const version string = "0.5.0.beta"
 
+var usage string = fmt.Sprintf(`Delve version %s
+
+flags:
+  -v - Print version
+
+Invoke with the path to a binary:
+
+dlv ./path/to/prog
+
+or use the following commands:
+  run - Build, run, and attach to program
+  attach - Attach to running process
+`, version)
+
 func init() {
 	// We must ensure here that we are running on the same thread during
 	// the execution of dbg. This is due to the fact that ptrace(2) expects
@@ -19,19 +33,12 @@ func init() {
 }
 
 func main() {
-	var (
-		pid    int
-		run    bool
-		printv bool
-	)
+	var printv bool
 
-	flag.IntVar(&pid, "pid", 0, "Pid of running process to attach to.")
-	flag.BoolVar(&run, "run", false, "Compile program and begin debug session.")
-	flag.BoolVar(&printv, "v", false, "Print version number and exit.")
 	flag.Parse()
 
 	if flag.NFlag() == 0 && len(flag.Args()) == 0 {
-		flag.Usage()
+		fmt.Println(usage)
 		os.Exit(0)
 	}
 
@@ -40,5 +47,5 @@ func main() {
 		os.Exit(0)
 	}
 
-	cli.Run(run, pid, flag.Args())
+	cli.Run(os.Args[1:])
 }