utility to check an output file and stop the program when the desired size is reached

monitor.go

// This utility allows you to run a command which produce a file and interrup it when a certain size is reached
package main
 
import(
        "flag"
        "fmt"
        "log"
        "os"
        "os/exec"
        "time"
)
 
func main(){
        interval := flag.Int("i",200,"check interval")
        delay := flag.Int("d",5,"initial delay")
        size := flag.Int("s",5000,"desired file size")
        filename := flag.String("f","","file to monitor")
        tool := flag.String("c","","command to run")
        flag.Parse()
 
        ticker := time.NewTicker(time.Duration(*interval) * time.Millisecond)

	//this goroutine checks the size of the file 
        go func() {
                time.Sleep(time.Duration(*delay) * time.Duration(*interval) * time.Millisecond)
                fmt.Println("Watcher started")
                for {
                        select {
                                case <- ticker.C :
                                        stat, err := os.Stat(*filename)
                                        if err != nil {
                                                log.Fatal(err)
                                        }
                                        fmt.Printf("size: %d\n", stat.Size() )
                                        if stat.Size() > int64(*size) {
                                                fmt.Println("Desired size reached!")
                                                os.Exit(0)
                                        }
                                }
                        }
        }()
 
	//this goroutine runs the command which will produce the file we want
        go func() {
                fmt.Println("Running %v", *tool)
                cmd := exec.Command("sh","-c",*tool)
                return_value := cmd.Run()
                log.Printf("Command returned: %v", return_value)
        }()
 
        for{
        }
 
}