Download webms and save it to a folder with ffmpeg

main.go

package main

import (
	"crypto/rand"
	"fmt"
	"os"
	"os/exec"
	"strings"
)

// https://stackoverflow.com/a/67035900
var chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890-"

func shortID(length int) string {
	ll := len(chars)
	b := make([]byte, length)
	rand.Read(b) // generates len(b) random bytes
	for i := 0; i < length; i++ {
		b[i] = chars[int(b[i])%ll]
	}
	return string(b)
}

func main() {
	s := strings.Join([]string{"D:/webms/", shortID(10), ".mp4"}, "")
	cmd := exec.Command("ffmpeg", "-fflags", "+genpts", "-i", os.Args[1], "-r", "24", s)
	stdout, err := cmd.Output()
	if err != nil {
		fmt.Println("Unable to download file.")
		fmt.Println(err)
		return
	}
	fmt.Println("Downloaded file:", s)
	fmt.Println(string(stdout))
}