list files from a tar archive

process-tar.go

package main

// tweaked from
// original source: https://gist.github.com/indraniel/1a91458984179ab4cf80

import (
	"archive/tar"
	"compress/gzip"
	"flag"
	"fmt"
	"io"
	"os"
)

func main() {
	flag.Parse()

	sourceFile := flag.Arg(0)

	if sourceFile == "" {
		fmt.Println("Dude, you didn't pass in a tar file!")
		os.Exit(1)
	}

	processFile(sourceFile)
}

func processFile(srcFile string) {
	f, err := os.Open(srcFile)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	defer f.Close()

	var source io.Reader

	// make a gzip reader
	gzf, err := gzip.NewReader(f)
	if err != nil {
		fmt.Println("Doesn't look like it is compressed...pretending it is a raw tar")
		source = f
	} else {
		source = gzf
	}

	// make a tar reader
	tarReader := tar.NewReader(source)

	for {
		header, err := tarReader.Next()

		if err == io.EOF {
			break
		}

		if err != nil {
			fmt.Println(err)
			os.Exit(1)
		}

		switch header.Typeflag {
		case tar.TypeDir:
			continue
		case tar.TypeReg:
			fmt.Println("File:", header.Name)
		default:
			fmt.Printf("%s : %c %s %s\n",
				"Yikes! Unable to figure out type",
				header.Typeflag,
				"in file",
				header.Name,
			)
		}

	}
}

The point was to process the tar.gz while it was uploading. You don't have to wait for the whole file, write it to disk and then decompress it. The file structure of tar.gz files allow you to process them as a stream.