Creating TAR Archives in Go

A short program to show how to write TAR-GZ and TAR-XZ (LZMA) archives. Note that I have not included an example for TAR-BZ2 because there is no easily-findable public library for doing so.

package main

import (
    "archive/tar"
    "compress/gzip"

    "fmt"
    "os"
    "io"
    "time"

    "github.com/ulikunitz/xz"
)

func addFile(tw *tar.Writer, filepath string) {
    data := fmt.Sprintf("I am data: %s\n", filepath)

    h := new(tar.Header)
    h.Name = filepath
    h.Size = int64(len(data))
    h.Mode =  int64(0666)
    h.ModTime = time.Now()

    // write the header to the tarball archive
    if err := tw.WriteHeader(h); err != nil {
        panic(err)
    }

    // copy the file data to the tarball 
    if _, err := io.WriteString(tw, data); err != nil {
        panic(err)
    }
}

func createTarGz() {
    f, err := os.Create("output.tar.gz")
    if err != nil {
        panic(err)
    }

    defer f.Close()

    gw := gzip.NewWriter(f)
    defer gw.Close()

    tw := tar.NewWriter(gw)
    defer tw.Close()

    addFile(tw, "aa")
    addFile(tw, "bb/cc")
}

func createTarXz() {
    f, err := os.Create("output.tar.xz")
    if err != nil {
        panic(err)
    }

    defer f.Close()

    xw, err := xz.NewWriter(f)
    if err != nil {
        panic(err)
    }

    defer xw.Close()

    tw := tar.NewWriter(xw)
    defer tw.Close()

    addFile(tw, "dd")
    addFile(tw, "ee/ff")
}

func main() {
    createTarGz()
    createTarXz()
}

Examine the outputs:

$ tar tzf output.tar.gz 
aa
bb/cc
$ tar xz -O - -f output.tar.gz aa
I am data: aa
$ tar xz -O - -f output.tar.gz bb/cc
I am data: bb/cc

$ tar tJf output.tar.xz
dd
ee/ff
I am data: bb/cc
$ tar xJ -O - -f output.tar.xz dd
I am data: dd
$ tar xJ -O - -f output.tar.xz ee/ff
I am data: ee/ff
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