tar - ActiveState ActiveGo 1.8

Package tar

import "archive/tar"

Overview ▾

Package tar implements access to tar archives. It aims to cover most of the variations, including those produced by GNU and BSD tars.





// Create a buffer to write our archive to.
buf := new(bytes.Buffer)

// Create a new tar archive.
tw := tar.NewWriter(buf)

// Add some files to the archive.
var files = []struct {
    Name, Body string
    {"readme.txt", "This archive contains some text files."},
    {"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo"},
    {"todo.txt", "Get animal handling license."},
for _, file := range files {
    hdr := &tar.Header{
        Name: file.Name,
        Mode: 0600,
        Size: int64(len(file.Body)),
    if err := tw.WriteHeader(hdr); err != nil {
    if _, err := tw.Write([]byte(file.Body)); err != nil {
// Make sure to check the error on Close.
if err := tw.Close(); err != nil {

// Open the tar archive for reading.
r := bytes.NewReader(buf.Bytes())
tr := tar.NewReader(r)

// Iterate through the files in the archive.
for {
    hdr, err := tr.Next()
    if err == io.EOF {
        // end of tar archive
    if err != nil {
    fmt.Printf("Contents of %s:\n", hdr.Name)
    if _, err := io.Copy(os.Stdout, tr); err != nil {


Contents of readme.txt:
This archive contains some text files.
Contents of gopher.txt:
Gopher names:
Contents of todo.txt:
Get animal handling license.


Header type flags.

const (
    TypeReg           = '0'    // regular file
    TypeRegA          = '\x00' // regular file
    TypeLink          = '1'    // hard link
    TypeSymlink       = '2'    // symbolic link
    TypeChar          = '3'    // character device node
    TypeBlock         = '4'    // block device node
    TypeDir           = '5'    // directory
    TypeFifo          = '6'    // fifo node
    TypeCont          = '7'    // reserved
    TypeXHeader       = 'x'    // extended header
    TypeXGlobalHeader = 'g'    // global extended header
    TypeGNULongName   = 'L'    // Next file has a long name
    TypeGNULongLink   = 'K'    // Next file symlinks to a file w/ a long name
    TypeGNUSparse     = 'S'    // sparse file


var (
    ErrWriteTooLong    = errors.New("archive/tar: write too long")
    ErrFieldTooLong    = errors.New("archive/tar: header field too long")
    ErrWriteAfterClose = errors.New("archive/tar: write after close")
var (
    ErrHeader = errors.New("archive/tar: invalid tar header")

A Header represents a single header in a tar archive. Some fields may not be populated.

type Header struct {
    Name       string    // name of header file entry
    Mode       int64     // permission and mode bits
    Uid        int       // user id of owner
    Gid        int       // group id of owner
    Size       int64     // length in bytes
    ModTime    time.Time // modified time
    Typeflag   byte      // type of header entry
    Linkname   string    // target name of link
    Uname      string    // user name of owner
    Gname      string    // group name of owner
    Devmajor   int64     // major number of character or block device
    Devminor   int64     // minor number of character or block device
    AccessTime time.Time // access time
    ChangeTime time.Time // status change time
    Xattrs     map[string]string

func FileInfoHeader

func FileInfoHeader(fi os.FileInfo, link string) (*Header, error)

FileInfoHeader creates a partially-populated Header from fi. If fi describes a symlink, FileInfoHeader records link as the link target. If fi describes a directory, a slash is appended to the name. Because os.FileInfo's Name method returns only the base name of the file it describes, it may be necessary to modify the Name field of the returned header to provide the full path name of the file.

func (*Header) FileInfo

func (h *Header) FileInfo() os.FileInfo

FileInfo returns an os.FileInfo for the Header.

type Reader

A Reader provides sequential access to the contents of a tar archive. A tar archive consists of a sequence of files. The Next method advances to the next file in the archive (including the first), and then it can be treated as an io.Reader to access the file's data.

type Reader struct {
    // contains filtered or unexported fields

func NewReader

func NewReader(r io.Reader) *Reader

NewReader creates a new Reader reading from r.

func (*Reader) Next

func (tr *Reader) Next() (*Header, error)

Next advances to the next entry in the tar archive.

io.EOF is returned at the end of the input.

func (*Reader) Read

func (tr *Reader) Read(b []byte) (int, error)

Read reads from the current entry in the tar archive. It returns 0, io.EOF when it reaches the end of that entry, until Next is called to advance to the next entry.

Calling Read on special types like TypeLink, TypeSymLink, TypeChar, TypeBlock, TypeDir, and TypeFifo returns 0, io.EOF regardless of what the Header.Size claims.

type Writer

A Writer provides sequential writing of a tar archive in POSIX.1 format. A tar archive consists of a sequence of files. Call WriteHeader to begin a new file, and then call Write to supply that file's data, writing at most hdr.Size bytes in total.

type Writer struct {
    // contains filtered or unexported fields

func NewWriter

func NewWriter(w io.Writer) *Writer

NewWriter creates a new Writer writing to w.

func (*Writer) Close

func (tw *Writer) Close() error

Close closes the tar archive, flushing any unwritten data to the underlying writer.

func (*Writer) Flush

func (tw *Writer) Flush() error

Flush finishes writing the current file (optional).

func (*Writer) Write

func (tw *Writer) Write(b []byte) (n int, err error)

Write writes to the current entry in the tar archive. Write returns the error ErrWriteTooLong if more than hdr.Size bytes are written after WriteHeader.

func (*Writer) WriteHeader

func (tw *Writer) WriteHeader(hdr *Header) error

WriteHeader writes hdr and prepares to accept the file's contents. WriteHeader calls Flush if it is not the first header. Calling after a Close will return ErrWriteAfterClose.