Commandline hotkey tool. Usage: `hotkey F12 say hello`

hotkey.go

package main

// #cgo LDFLAGS: -framework Carbon
// #include <Carbon/Carbon.h>
// extern void Callback();
// void RunApplicationEventLoop();
// static inline OSStatus handler(EventHandlerCallRef nextHandler, EventRef theEvent, void* userData)
// {
//   Callback();
//   return 1;
// }
// static inline int Register(int key) {
//   EventTypeSpec eventType;
//   eventType.eventClass = kEventClassKeyboard;
//   eventType.eventKind  = kEventHotKeyPressed;
//
//   InstallApplicationEventHandler(&handler, 1, &eventType, NULL, NULL);
//
//   EventHotKeyID g_HotKeyID;
//   g_HotKeyID.id = 1;
//
//   EventHotKeyRef g_HotKeyRef;
//
//   RegisterEventHotKey(key, 0, g_HotKeyID, GetApplicationEventTarget(), 0, &g_HotKeyRef);
//
//   return 0;
// }
// static inline void Run() {
//   RunApplicationEventLoop();
// }
import "C"
import (
	"flag"
	"fmt"
	"os"
	"os/exec"
	"strings"
)

// Callback is called by the C binding
//export Callback
func Callback() {
	if verbose {
		fmt.Println(keyName, "pressed! running:", command)
	}
	cmd := exec.Command(command[0], command[1:]...)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	err := cmd.Run()
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
	}
}

var keys = map[string]C.int{
	"f1": C.kVK_F1, "f2": C.kVK_F2, "f3": C.kVK_F3, "f4": C.kVK_F4,
	"f5": C.kVK_F5, "f6": C.kVK_F6, "f7": C.kVK_F7, "f8": C.kVK_F8,
	"f9": C.kVK_F9, "f10": C.kVK_F10, "f11": C.kVK_F11, "f12": C.kVK_F12,
	"f13": C.kVK_F13, "f14": C.kVK_F14, "f15": C.kVK_F15, "f16": C.kVK_F16,
	"f17": C.kVK_F17, "f18": C.kVK_F18, "f19": C.kVK_F19, "f20": C.kVK_F20,
}

var verbose bool
var keyName string
var command []string

func main() {
	flag.Usage = func() {
		fmt.Println("  usage: hotkey [-v] KEY COMMAND [ARGS...]")
		fmt.Println("example: hotkey F12 echo hello")
	}
	flag.BoolVar(&verbose, "v", false, "output key presses")
	flag.Parse()
	if flag.NArg() < 2 {
		flag.Usage()
		os.Exit(1)
	}
	args := flag.Args()
	keyName = args[0]
	command = args[1:]
	key, found := keys[strings.ToLower(keyName)]
	if !found {
		fmt.Fprintf(os.Stderr, "error: key not supported: %s\n", keyName)
		os.Exit(1)
	}

	C.Register(key)
	C.Run()
}