restart the command when the file changes.

only works when the program has no errors, i think.

go/qst.go

@@ -7,6 +7,7 @@ import "os"
import "os/exec"
import "path"
import "strings"
import "sync"
import "time"
/*
@@ -30,6 +31,8 @@ var mappings = map[string]func(string) string{
}
func main() {
	log.SetFlags(log.Ldate | log.Ltime | log.Lshortfile)
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: %s <file>\n", os.Args[0])
		flag.PrintDefaults()
@@ -59,9 +62,12 @@ func main() {
	}
}
func runAndWatch(file string, cmd string) {
func runAndWatch(file string, cmdLine string) {
	// run command, if file changes (mtime) restart command
	lastMtime := time.Unix(0, 0)
	lastMtime := time.Now()
	cmd := ShellCmd(cmdLine)
	cmd.Start()
	for {
		info, err := os.Stat(file)
		if err != nil {
@@ -71,7 +77,7 @@ func runAndWatch(file string, cmd string) {
		mtime := info.ModTime()
		if mtime.After(lastMtime) {
			log.Printf("%s changed, rerunning", file)
			runShellCmd(cmd)
			cmd.Restart()
		}
		lastMtime = mtime
@@ -79,6 +85,31 @@ func runAndWatch(file string, cmd string) {
	}
}
type RestartableCommand struct {
	Cmd  *exec.Cmd
	Lock sync.Mutex
	Name string
	Args []string
}
func ShellCmd(cmd string) RestartableCommand {
	return RestartableCommand{nil, sync.Mutex{}, "sh", []string{"-c", cmd}}
}
func (c *RestartableCommand) Start() {
	c.Cmd = exec.Command(c.Name, c.Args...)
	c.Lock.Lock()
	go func() {
		c.Cmd.Run()
		c.Lock.Unlock()
	}()
}
func (c *RestartableCommand) Restart() {
	c.Cmd.Process.Kill()
	c.Start()
}
func runShellCmd(cmd string) {
	log.Printf("Running: `%s'", cmd)
	output, err := exec.Command("sh", "-c", cmd).CombinedOutput()