untar-to-memory

npm module for reading stuff from tarballs without writing to the filesystem.

The aim of this module is to mimic the read-oriented behavior of command-line tar.

Command-line tar takes a multitude of options, not all of which are currently implemented in this module.

Installation

npm install untar-to-memory

There are optional dependencies that provide decompression of bzip2-, LZMA-, and XZ-compressed tarballs. If your project will rely on one of these, be sure to install them as regular dependencies instead of using --include optional when you install untar-to-memory:

npm install unbzip2-stream

For LZMA and/or XZ:

npm install lzma-native

Usage

const untar = require('untar-to-memory')

const tgzPath = path.resolve("path", "to", "tarball1.tgz")

// Verbatim entry specification - options omitted gets defaults
untar.readEntry(tgzPath, "secret/passwords.bin").then(buf => {
  // ...
})

const tarPath = path.resolve("another", "path", "tarball2.tar")
const opts = { ignoreCase: true, wildcards: true, wildcardsMatchSlash: false }

// Get the contents of the first "keys.txt" entry that is directly under a
// top level directory in the tarball, regardless of the entry name case:
untar.readEntry(tarPath, "*/KEYS.TXT", opts).then(buf => {
  // ...
})

// Get list of all entries from tarball2.tar
untar.list(tarPath).then(allEntries => {
  for (let i = 0; i < allEntries.length; i++) {
    // ...
  }
})

// Get list of only the entries directly under "secret/" in tarball1.tgz
const opts = {
  pattern: "secret/*", wildcards: true, wildcardsMatchSlash: false,
  recursion: false
}
untar.list(tgzPath, opts).then(topSecrets => {
  // ...
})

API

Both methods return Promises. Some possible error codes if the Promise rejects are:

• EINVAL: invalid argument/option value.
• EFTYPE: the tarball has an invalid entry, or the file type is not recognized.
• ENOENT: the tarball path was not found.
• ENOMATCH: no entry was found to match the entry path/pattern as given.
• EFBIG (readEntry only): the matching entry is bigger than the maxSize set by the user.

readEntry (tarball, filename, options) → Promise<Buffer>

• tarball {string}: path to a tar archive, which may or may not be compressed.

• filename {string}: path pattern to match an entry in the tarball.

• options {object}: settings to control pattern matching. Mostly corresponding to command-line tar options.

  Valid fields:

  • anchored: default true
  • ignoreCase: default false
  • maxSize: default 0 (meaning unlimited)
  • recursion: default true
  • useCompressProgram/I: default '' (autodetection for gzip)
    • other valid values are 'bzip', 'gzip', 'lzma', 'xz'
  • bzip/gzip/lzma/xz: default false
  • wildcards: default false
  • wildcardsMatchSlash: default false, true if wildcards is true

Resolves to a Buffer holding the contents of the entry if successful.

Use of this function roughly corresponds to using operation mode x (--extract, --get) of command-line tar with option -O (--to-stdout) to extract a single specified file.

list (tarball, options) → Promise<Array>

• tarball {string}: path to a tar archive, which may or may not be compressed.

• options {object}: settings to control pattern matching. Mostly corresponding to command-line tar options.

  Valid fields:

  • anchored: default true
  • ignoreCase: default false
  • pattern: default ''; if empty, all entries will be matched.
  • recursion: default true
  • useCompressProgram/I: default '' (autodetection for gzip)
    • other valid values are 'bzip', 'gzip', 'lzma', 'xz'
  • bzip/gzip/lzma/xz: default false
  • wildcards: default false
  • wildcardsMatchSlash: default false, true if wildcards is true

Resolves to an array of matched entry paths (possibly empty) if successful.
It is not treated as an error if there are no matches.

Pattern Matching Control

For an authoritative discussion and examples, see the tar manual page at gnu.org

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License: Artistic 2.0