installsubl.go

package main

import (
	"archive/tar"
	"compress/bzip2"
	"flag"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
)

var (
	url     = "http://www.sublimetext.com/3dev"
	pattern = regexp.MustCompile(`Ubuntu 64 bit.*<a href="(.*_x64\.tar\.bz2)"`)

	flagPath = flag.String("path", "", "path to write out")
)

func getHref() string {
	resp, err := http.Get(url)
	if err != nil {
		log.Fatalf("http.Get failed: %v\n", err)
	}
	b, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		log.Fatalf("ioutil.ReadAll failed: %v\n", err)
	}
	m := pattern.FindSubmatch(b)
	if len(m) != 2 {
		log.Fatalf("Failed to locate href: %s", m)
	}
	href := m[1]
	return string(href)
}

func download(href string) *http.Response {
	resp, err := http.Get(href)
	if err != nil {
		log.Fatalf("http.Get failed: %v\n", err)
	}
	return resp
}

func expand(r io.Reader, path string) (dir string) {
	tr := tar.NewReader(bzip2.NewReader(r))
	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatalf("Error reading tar header: %s\n", err)
		}
		dst := filepath.Join(path, hdr.Name)

		if dir == "" {
			dir = dst
		}

		switch hdr.Typeflag {
		case tar.TypeDir:
			err := os.MkdirAll(dst, 0766)
			if err != nil {
				log.Fatalf("Failed to create folder: %s\n", err)
			}
		default:
			out, err := os.OpenFile(dst, os.O_RDWR|os.O_CREATE|os.O_TRUNC, os.FileMode(hdr.Mode))
			if err != nil {
				log.Fatalf("Failed to create destination: %s\n", err)
			}
			if _, err := io.Copy(out, tr); err != nil {
				log.Fatalf("Failed to write file to disk: ", err)
			}
		}
	}
	return
}

func main() {
	flag.Parse()
	if *flagPath == "" {
		flag.Usage()
		return
	}

	log.Println("retrieving link")
	href := getHref()
	log.Println("downloading archive")
	resp := download(href)
	log.Println("expanding archive")
	_ = expand(resp.Body, *flagPath)
	log.Println("done!")
}