isaacs/node-tar

node-tar

Fast and full-featured Tar for Node.js

The API is designed to mimic the behavior of tar(1) on unix systems. If you are familiar with how tar works, most of this will hopefully be straightforward for you. If not, then hopefully this module can teach you useful unix skills that may come in handy someday :)

Security Information

Significant efforts have been taken to harden this library against a wide variety of filesystem based attacks, especially as it is used to unpack packages that are published by unknown agents to the npm registry.

A brief overview of some of the hardening that has gone into this implementation. (Note that most of these are disabled if preservePaths: true is set in the options.)

• Paths that attempt to walk up outside of the extraction target are ignored, and a warning is raised.
• Link and SymbolicLink entries are not allowed to target locations outside of the extraction folder.
• Extraction is not allowed through a symbolic link that appears within the extraction target.
• Absolute paths are turned into relative paths underneath the extraction target.
• Character Device, Block Device, and FIFO entries are never extracted.
• File and directory ownership is not mutated unless forceChown is set, or the extraction is run as root.
• File and directory modes in the archive are ignored, unless the chmod: true option is set.
• A path-reservation system is used to ensure that even when multiple entries are being extracted in parallel, subsequent entries with the same filename will not interfere with one another (for example, exchanging a file with a symbolic link while it is being written to).
• Unicode characters in path names are fully normalized, to prevent evading these protections with unicode equivalences.

It is frankly unlikely that any tar implementation in JavaScript is going to be as secure as this one, unless a similar amount of work is put into it, putting it to the test over many years of intensive use and scrutiny. You can vibe-code a tar extractor in an afternoon, but you'll regret it.

[!WARNING]

However, all that being said, care must still be taken when dealing with data from unknown sources, especially when extracting files, with this or any library, no matter how hardened it may be. It is your responsibility to use this library safely.

1. NEVER extract tarball data into a folder that could be potentially controlled by an unknown actor. A clever attacker can swap out the target of an extracted file with a symbolic link to some location of their choosing, resulting in writing files outside the target folder. There is no reasonable way to harden against this category of attack, and security reports about it will be closed. TOCTOU exposure is unavoidable when creating files based on entries in an archive file.
2. If you are unpacking tarballs that may come from an unknown source, it is highly recommended that you use a filter function that rejects all hardlinks and symbolic links. Link files are historically the root of nearly every file extraction vulnerability. (npm filters links out of package artifacts for this reason.)
3. If you are extracting tarballs that are compressed (eg, with gzip, brotli, or zstd), then it is a very good idea to also filter out any files that are excessively large. Even if you are restricting the size of the archive file itself, an excessively large file of repetitive data can compress down very small, and extract to take up a lot of disk space.
4. Stay up to date. Old versions of tar are not maintained or tested for newly discovered security advisories, and should be assumed to contain every known security vulnerability, and many that are unknown.

If you find a security vulnerability in node-tar, where it is not properly enforcing the intended security protections, then please report it using the GitHub Security Advisories system, where it will be triaged and corrected if possible.

Background

A "tar file" or "tarball" is an archive of file system entries (directories, files, links, etc.) The name comes from "tape archive". If you run man tar on almost any Unix command line, you'll learn quite a bit about what it can do, and its history.

Tar has 5 main top-level commands:

• c Create an archive
• r Replace entries within an archive
• u Update entries within an archive (ie, replace if they're newer)
• t List out the contents of an archive
• x Extract an archive to disk

The other flags and options modify how this top level function works.

High-Level API

These 5 functions are the high-level API. All of them have a single-character name (for unix nerds familiar with tar(1)) as well as a long name (for everyone else).

All the high-level functions take the following arguments, all three of which are optional and may be omitted.

1. options - An optional object specifying various options
2. paths - An array of paths to add or extract
3. callback - Called when the command is completed, if async. (If sync or no file specified, providing a callback throws a TypeError.)

If the command is sync (ie, if options.sync=true), then the callback is not allowed, since the action will be completed immediately.

If a file argument is specified, and the command is async, then a Promise is returned. In this case, if async, a callback may be provided which is called when the command is completed.

If a file option is not specified, then a stream is returned. For create, this is a readable stream of the generated archive. For list and extract this is a writable stream that an archive should be written into. If a file is not specified, then a callback is not allowed, because you're already getting a stream to work with.

replace and update only work on existing archives, and so require a file argument.

Sync commands without a file argument return a stream that acts on its input immediately in the same tick. For readable streams, this means that all of the data is immediately available by calling stream.read(). For writable streams, it will be acted upon as soon as it is provided, but this can be at any time.

Warnings and Errors

Tar emits warnings and errors for recoverable and unrecoverable situations, respectively. In many cases, a warning only affects a single entry in an archive, or is simply informing you that it's modifying an entry to comply with the settings provided.

Unrecoverable warnings will always raise an error (ie, emit 'error' on streaming actions, throw for non-streaming sync actions, reject the returned Promise for non-streaming async operations, or call a provided callback with an Error as the first argument). Recoverable errors will raise an error only if strict: true is set in the options.

Respond to (recoverable) warnings by listening to the warn event. Handlers receive 3 arguments:

• code String. One of the error codes below. This may not match data.code, which preserves the original error code from fs and zlib.
• message String. More details about the error.
• data Metadata about the error. An Error object for errors raised by fs and zlib. All fields are attached to errors raisd by tar. Typically contains the following fields, as relevant:
  • tarCode The tar error code.
  • code Either the tar error code, or the error code set by the underlying system.
  • file The archive file being read or written.
  • cwd Working directory for creation and extraction operations.
  • entry The entry object (if it could be created) for TAR_ENTRY_INFO, TAR_ENTRY_INVALID, and TAR_ENTRY_ERROR warnings.
  • header The header object (if it could be created, and the entry could not be created) for TAR_ENTRY_INFO and TAR_ENTRY_INVALID warnings.
  • recoverable Boolean. If false, then the warning will emit an error, even in non-strict mode.

Error Codes

• TAR_ENTRY_INFO An informative error indicating that an entry is being modified, but otherwise processed normally. For example, removing / or C:\ from absolute paths if preservePaths is not set.

• TAR_ENTRY_INVALID An indication that a given entry is not a valid tar archive entry, and will be skipped. This occurs when:

  • a checksum fails,
  • a linkpath is missing for a link type, or
  • a linkpath is provided for a non-link type.

  If every entry in a parsed archive raises an TAR_ENTRY_INVALID error, then the archive is presumed to be unrecoverably broken, and TAR_BAD_ARCHIVE will be raised.

• TAR_ENTRY_ERROR The entry appears to be a valid tar archive entry, but encountered an error which prevented it from being unpacked. This occurs when:

  • an unrecoverable fs error happens during unpacking,
  • an entry is trying to extract into an excessively deep location (by default, limited to 1024 subfolders),
  • an entry has .. in the path and preservePaths is not set, or
  • an entry is extracting through a symbolic link, when preservePaths is not set.

• TAR_ENTRY_UNSUPPORTED An indication that a given entry is a valid archive entry, but of a type that is unsupported, and so will be skipped in archive creation or extracting.

• TAR_ABORT When parsing gzipped-encoded archives, the parser will abort the parse process raise a warning for any zlib errors encountered. Aborts are considered unrecoverable for both parsing and unpacking.

• TAR_BAD_ARCHIVE The archive file is totally hosed. This can happen for a number of reasons, and always occurs at the end of a parse or extract:

  • An entry body was truncated before seeing the full number of bytes.
  • The archive contained only invalid entries, indicating that it is likely not an archive, or at least, not an archive this library can parse.

  TAR_BAD_ARCHIVE is considered informative for parse operations, but unrecoverable for extraction. Note that, if encountered at the end of an extraction, tar WILL still have extracted as much it could from the archive, so there may be some garbage files to clean up.

Errors that occur deeper in the system (ie, either the filesystem or zlib) will have their error codes left intact, and a tarCode matching one of the above will be added to the warning metadata or the raised error object.

Errors generated by tar will have one of the above codes set as the error.code field as well, but since errors originating in zlib or fs will have their original codes, it's better to read error.tarCode if you wish to see how tar is handling the issue.

Examples

The API mimics the tar(1) command line functionality, with aliases for more human-readable option and function names. The goal is that if you know how to use tar(1) in Unix, then you know how to use import('tar') in JavaScript.

To replicate tar czf my-tarball.tgz files and folders, you'd do:

import { create } from 'tar'
create(
  {
    gzip: <true|gzip options>,
    file: 'my-tarball.tgz'
  },
  ['some', 'files', 'and', 'folders']
).then(_ => { .. tarball has been created .. })

To replicate tar cz files and folders > my-tarball.tgz, you'd do:

// if you're familiar with the tar(1) cli flags, this can be nice
import * as tar from 'tar'
tar.c(
  {
    // 'z' is alias for 'gzip' option
    z: <true|gzip options>
  },
  ['some', 'files', 'and', 'folders']
).pipe(fs.createWriteStream('my-tarball.tgz'))

To replicate tar xf my-tarball.tgz you'd do:

tar.x( // or `tar.extract`
  {
    // or `file:`
    f: 'my-tarball.tgz'
  }
).then(_=> { .. tarball has been dumped in cwd .. })

To replicate cat my-tarball.tgz | tar x -C some-dir --strip=1:

fs.createReadStream('my-tarball.tgz').pipe(
  tar.x({
    strip: 1,
    C: 'some-dir', // alias for cwd:'some-dir', also ok
  }),
)

To replicate tar tf my-tarball.tgz, do this:

tar.t({
  file: 'my-tarball.tgz',
  onReadEntry: entry => { .. do whatever with it .. }
})

For example, to just get the list of filenames from an archive:

const getEntryFilenames = async tarballFilename => {
  const filenames = []
  await tar.t({
    file: tarballFilename,
    onReadEntry: entry => filenames.push(entry.path),
  })
  return filenames
}

To replicate cat my-tarball.tgz | tar t do:

fs.createReadStream('my-tarball.tgz')
  .pipe(tar.t())
  .on('entry', entry => { .. do whatever with it .. })

To do anything synchronous, add sync: true to the options. Note that sync functions don't take a callback and don't return a promise. When the function returns, it's already done. Sync methods without a file argument return a sync stream, which flushes immediately. But, of course, it still won't be done until you .end() it.

const getEntryFilenamesSync = tarballFilename => {
  const filenames = []
  tar.t({
    file: tarballFilename,
    onReadEntry: entry => filenames.push(entry.path),
    sync: true,
  })
  return filenames
}

To filter entries, add filter: <function> to the options. Tar-creating methods call the filter with filter(path, stat). Tar-reading methods (including extraction) call the filter with filter(path, entry). The filter is called in the this-context of the Pack or Unpack stream object.

The arguments list to tar t and tar x specify a list of filenames to extract or list, so they're equivalent to a filter that tests if the file is in the list.

For those who aren't fans of tar's single-character command names:

tar.c === tar.create
tar.r === tar.replace (appends to archive, file is required)
tar.u === tar.update (appends if newer, file is required)
tar.x === tar.extract
tar.t === tar.list

Keep reading for all the command descriptions and options, as well as the low-level API that they are built on.

tar.c(options, fileList, callback) [alias: tar.create]

Create a tarball archive.

The fileList is an array of paths to add to the tarball. Adding a directory also adds its children recursively.

An entry in fileList that starts with an @ symbol is a tar archive whose entries will be added. To add a file that starts with @, prepend it with ./.

The following options are supported:

• file Write the tarball archive to the specified filename. If this is specified, then the callback will be fired when the file has been written, and a promise will be returned that resolves when the file is written. If a filename is not specified, then a Readable Stream will be returned which will emit the file data. [Alias: f]
• sync Act synchronously. If this is set, then any provided file will be fully written after the call to tar.c. If this is set, and a file is not provided, then the resulting stream will already have the data ready to read or emit('data') as soon as you request it.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• strict Treat warnings as crash-worthy errors. Default false.
• cwd The current working directory for creating the archive. Defaults to process.cwd(). [Alias: C]
• prefix A path portion to prefix onto the entries in the archive.
• gzip Set to any truthy value to create a gzipped archive, or an object with settings for zlib.Gzip() [Alias: z]
• filter A function that gets called with (path, stat) for each entry being added. Return true to add the entry to the archive, or false to omit it.
• portable Omit metadata that is system-specific: ctime, atime, uid, gid, uname, gname, dev, ino, and nlink. Note that mtime is still included, because this is necessary for other time-based operations. Additionally, mode is set to a "reasonable default" for most unix systems, based on a umask value of 0o22.
• preservePaths Allow absolute paths. By default, / is stripped from absolute paths. [Alias: P]
• mode The mode to set on the created file archive
• noDirRecurse Do not recursively archive the contents of directories. [Alias: n]
• follow Set to true to pack the targets of symbolic links. Without this option, symbolic links are archived as such. [Alias: L, h]
• noPax Suppress pax extended headers. Note that this means that long paths and linkpaths will be truncated, and large or negative numeric values may be interpreted incorrectly.
• noMtime Set to true to omit writing mtime values for entries. Note that this prevents using other mtime-based features like tar.update or the keepNewer option with the resulting tar archive. [Alias: m, no-mtime]
• mtime Set to a Date object to force a specific mtime for everything added to the archive. Overridden by noMtime.
• onWriteEntry Called with each WriteEntry or WriteEntrySync that is created in the course of writing the archive.

The following options are mostly internal, but can be modified in some advanced use cases, such as re-using caches between runs.

• linkCache A Map object containing the device and inode value for any file whose nlink is > 1, to identify hard links.
• statCache A Map object that caches calls lstat.
• readdirCache A Map object that caches calls to readdir.
• jobs A number specifying how many concurrent jobs to run. Defaults to 4.
• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 16 MB.

Using onWriteEntry to alter entries

The onWriteEntry function, if provided, will get a reference to each entry object on its way into the archive.

If any fields on this entry are changed, then these changes will be reflected in the entry that is written to the archive.

The return value of the function is ignored. All that matters is the final state of the entry object. This can also be used to track the files added to an archive, for example.

import * as tar from 'tar'
const filesAdded = []
tar.c(
  {
    sync: true,
    file: 'lowercase-executable.tar',
    onWriteEntry(entry) {
      // initially, it's uppercase and 0o644
      console.log('adding', entry.path, entry.stat.mode.toString(8))
      // make all the paths lowercase
      entry.path = entry.path.toLowerCase()
      // make the entry executable
      entry.stat.mode = 0o755
      // in the archive, it's lowercase and 0o755
      filesAdded.push([entry.path, entry.stat.mode.toString(8)])
    },
  },
  ['./bin'],
)
console.log('added', filesAdded)

Then, if the ./bin directory contained SOME-BIN, it would show up in the archive as:

$ node create-lowercase-executable.js
adding ./bin/SOME-BIN 644
added [[ './bin/some-bin', '755' ]]

$ tar cvf lowercase-executable.tar
-rwxr-xr-x  0 isaacs 20      47731 Aug 14 08:56 ./bin/some-bin

with a lowercase name and a mode of 0o755.

tar.x(options, fileList, callback) [alias: tar.extract]

Extract a tarball archive.

The fileList is an array of paths to extract from the tarball. If no paths are provided, then all the entries are extracted.

If the archive is gzipped, then tar will detect this and unzip it.

Note that all directories that are created will be forced to be writable, readable, and listable by their owner, to avoid cases where a directory prevents extraction of child entries by virtue of its mode.

Most extraction errors will cause a warn event to be emitted. If the cwd is missing, or not a directory, then the extraction will fail completely.

The following options are supported:

• cwd Extract files relative to the specified directory. Defaults to process.cwd(). If provided, this must exist and must be a directory. [Alias: C]
• file The archive file to extract. If not specified, then a Writable stream is returned where the archive data should be written. [Alias: f]
• sync Create files and directories synchronously.
• strict Treat warnings as crash-worthy errors. Default false.
• filter A function that gets called with (path, entry) for each entry being unpacked. Return true to unpack the entry from the archive, or false to skip it.
• newer Set to true to keep the existing file on disk if it's newer than the file in the archive. [Alias: keep-newer, keep-newer-files]
• keep Do not overwrite existing files. In particular, if a file appears more than once in an archive, later copies will not overwrite earlier copies. [Alias: k, keep-existing]
• preservePaths Allow absolute paths, paths containing .., and extracting through symbolic links. By default, / is stripped from absolute paths, .. paths are not extracted, and any file whose location would be modified by a symbolic link is not extracted. [Alias: P]
• unlink Unlink files before creating them. Without this option, tar overwrites existing files, which preserves existing hardlinks. With this option, existing hardlinks will be broken, as will any symlink that would affect the location of an extracted file. [Alias: U]
• strip Remove the specified number of leading path elements. Pathnames with fewer elements will be silently skipped. Note that the pathname is edited after applying the filter, but before security checks. [Alias: strip-components, stripComponents]
• preserveOwner If true, tar will set the uid and gid of extracted entries to the uid and gid fields in the archive. This defaults to true when run as root, and false otherwise. If false, then files and directories will be set with the owner and group of the user running the process. This is similar to -p in tar(1), but ACLs and other system-specific data is never unpacked in this implementation, and modes are set by default already. [Alias: p]
• uid Set to a number to force ownership of all extracted files and folders, and all implicitly created directories, to be owned by the specified user id, regardless of the uid field in the archive. Cannot be used along with preserveOwner. Requires also setting a gid option.
• gid Set to a number to force ownership of all extracted files and folders, and all implicitly created directories, to be owned by the specified group id, regardless of the gid field in the archive. Cannot be used along with preserveOwner. Requires also setting a uid option.
• noMtime Set to true to omit writing mtime value for extracted entries. [Alias: m, no-mtime]
• transform Provide a function that takes an entry object, and returns a stream, or any falsey value. If a stream is provided, then that stream's data will be written instead of the contents of the archive entry. If a falsey value is provided, then the entry is written to disk as normal. (To exclude items from extraction, use the filter option described above.)
• onReadEntry A function that gets called with (entry) for each entry that passes the filter.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• chmod Set to true to call fs.chmod() to ensure that the extracted file matches the entry mode. This may necessitate a call to the deprecated and thread-unsafe process.umask() method to determine the default umask value, unless a processUmask options is also provided. Otherwise tar will extract with whatever mode is provided, and let the process umask apply normally.
• processUmask Set to an explicit numeric value to avoid calling process.umask() when chmod: true is set.
• maxDepth The maximum depth of subfolders to extract into. This defaults to 1024. Anything deeper than the limit will raise a warning and skip the entry. Set to Infinity to remove the limitation.
• maxDecompressionRatio Defaults to 1000. The maximum ratio of decommpressed bytes to compressed bytes, in a compressed archive. Set to Infinity to allow explosive decompression.

The following options are mostly internal, but can be modified in some advanced use cases, such as re-using caches between runs.

• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 16 MB.
• umask Filter the modes of entries like process.umask().
• dmode Default mode for directories
• fmode Default mode for files
• maxMetaEntrySize The maximum size of meta entries that is supported. Defaults to 1 MB.

Note that using an asynchronous stream type with the transform option will cause undefined behavior in sync extractions. MiniPass-based streams are designed for this use case.

tar.t(options, fileList, callback) [alias: tar.list]

List the contents of a tarball archive.

The fileList is an array of paths to list from the tarball. If no paths are provided, then all the entries are listed.

If the archive is gzipped, then tar will detect this and unzip it.

If the file option is not provided, then returns an event emitter that emits entry events with tar.ReadEntry objects. However, they don't emit 'data' or 'end' events. (If you want to get actual readable entries, use the tar.Parser class instead.)

If a file option is provided, then the return value will be a promise that resolves when the file has been fully traversed in async mode, or undefined if sync: true is set. Thus, you must specify an onReadEntry method in order to do anything useful with the data it parses.

The following options are supported:

• file The archive file to list. If not specified, then a Writable stream is returned where the archive data should be written. [Alias: f]
• sync Read the specified file synchronously. (This has no effect when a file option isn't specified, because entries are emitted as fast as they are parsed from the stream anyway.)
• strict Treat warnings as crash-worthy errors. Default false.
• filter A function that gets called with (path, entry) for each entry being listed. Return true to emit the entry from the archive, or false to skip it.
• onReadEntry A function that gets called with (entry) for each entry that passes the filter. This is important for when file is set, because there is no other way to do anything useful with this method.
• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 16 MB.
• noResume By default, entry streams are resumed immediately after the call to onReadEntry. Set noResume: true to suppress this behavior. Note that by opting into this, the stream will never complete until the entry data is consumed.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• maxDecompressionRatio Defaults to 1000. The maximum ratio of decommpressed bytes to compressed bytes, in a compressed archive. Set to Infinity to allow explosive decompression.

tar.u(options, fileList, callback) [alias: tar.update]

Add files to an archive if they are newer than the entry already in the tarball archive.

The fileList is an array of paths to add to the tarball. Adding a directory also adds its children recursively.

An entry in fileList that starts with an @ symbol is a tar archive whose entries will be added. To add a file that starts with @, prepend it with ./.

The following options are supported:

• file Required. Write the tarball archive to the specified filename. [Alias: f]
• sync Act synchronously. If this is set, then any provided file will be fully written after the call to tar.c.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• strict Treat warnings as crash-worthy errors. Default false.
• cwd The current working directory for adding entries to the archive. Defaults to process.cwd(). [Alias: C]
• prefix A path portion to prefix onto the entries in the archive.
• gzip Set to any truthy value to create a gzipped archive, or an object with settings for zlib.Gzip() [Alias: z]
• filter A function that gets called with (path, stat) for each entry being added. Return true to add the entry to the archive, or false to omit it.
• portable Omit metadata that is system-specific: ctime, atime, uid, gid, uname, gname, dev, ino, and nlink. Note that mtime is still included, because this is necessary for other time-based operations. Additionally, mode is set to a "reasonable default" for most unix systems, based on a umask value of 0o22.
• preservePaths Allow absolute paths. By default, / is stripped from absolute paths. [Alias: P]
• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 16 MB.
• noDirRecurse Do not recursively archive the contents of directories. [Alias: n]
• follow Set to true to pack the targets of symbolic links. Without this option, symbolic links are archived as such. [Alias: L, h]
• noPax Suppress pax extended headers. Note that this means that long paths and linkpaths will be truncated, and large or negative numeric values may be interpreted incorrectly.
• noMtime Set to true to omit writing mtime values for entries. Note that this prevents using other mtime-based features like tar.update or the keepNewer option with the resulting tar archive. [Alias: m, no-mtime]
• mtime Set to a Date object to force a specific mtime for everything added to the archive. Overridden by noMtime.
• onWriteEntry Called with each WriteEntry or WriteEntrySync that is created in the course of writing the archive.

tar.r(options, fileList, callback) [alias: tar.replace]

Add files to an existing archive. Because later entries override earlier entries, this effectively replaces any existing entries.

The fileList is an array of paths to add to the tarball. Adding a directory also adds its children recursively.

An entry in fileList that starts with an @ symbol is a tar archive whose entries will be added. To add a file that starts with @, prepend it with ./.

The following options are supported:

• file Required. Write the tarball archive to the specified filename. [Alias: f]
• sync Act synchronously. If this is set, then any provided file will be fully written after the call to tar.c.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• strict Treat warnings as crash-worthy errors. Default false.
• cwd The current working directory for adding entries to the archive. Defaults to process.cwd(). [Alias: C]
• prefix A path portion to prefix onto the entries in the archive.
• gzip Set to any truthy value to create a gzipped archive, or an object with settings for zlib.Gzip() [Alias: z]
• filter A function that gets called with (path, stat) for each entry being added. Return true to add the entry to the archive, or false to omit it.
• portable Omit metadata that is system-specific: ctime, atime, uid, gid, uname, gname, dev, ino, and nlink. Note that mtime is still included, because this is necessary for other time-based operations. Additionally, mode is set to a "reasonable default" for most unix systems, based on a umask value of 0o22.
• preservePaths Allow absolute paths. By default, / is stripped from absolute paths. [Alias: P]
• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 16 MB.
• noDirRecurse Do not recursively archive the contents of directories. [Alias: n]
• follow Set to true to pack the targets of symbolic links. Without this option, symbolic links are archived as such. [Alias: L, h]
• noPax Suppress pax extended headers. Note that this means that long paths and linkpaths will be truncated, and large or negative numeric values may be interpreted incorrectly.
• noMtime Set to true to omit writing mtime values for entries. Note that this prevents using other mtime-based features like tar.update or the keepNewer option with the resulting tar archive. [Alias: m, no-mtime]
• mtime Set to a Date object to force a specific mtime for everything added to the archive. Overridden by noMtime.
• onWriteEntry Called with each WriteEntry or WriteEntrySync that is created in the course of writing the archive.

Low-Level API

class Pack

A readable tar stream.

Has all the standard readable stream interface stuff. 'data' and 'end' events, read() method, pause() and resume(), etc.

constructor(options)

The following options are supported:

• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• strict Treat warnings as crash-worthy errors. Default false.
• cwd The current working directory for creating the archive. Defaults to process.cwd().
• prefix A path portion to prefix onto the entries in the archive.
• gzip Set to any truthy value to create a gzipped archive, or an object with settings for zlib.Gzip()
• filter A function that gets called with (path, stat) for each entry being added. Return true to add the entry to the archive, or false to omit it.
• portable Omit metadata that is system-specific: ctime, atime, uid, gid, uname, gname, dev, ino, and nlink. Note that mtime is still included, because this is necessary for other time-based operations. Additionally, mode is set to a "reasonable default" for most unix systems, based on a umask value of 0o22.
• preservePaths Allow absolute paths. By default, / is stripped from absolute paths.
• linkCache A Map object containing the device and inode value for any file whose nlink is > 1, to identify hard links.
• statCache A Map object that caches calls lstat.
• readdirCache A Map object that caches calls to readdir.
• jobs A number specifying how many concurrent jobs to run. Defaults to 4.
• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 16 MB.
• noDirRecurse Do not recursively archive the contents of directories.
• follow Set to true to pack the targets of symbolic links. Without this option, symbolic links are archived as such.
• noPax Suppress pax extended headers. Note that this means that long paths and linkpaths will be truncated, and large or negative numeric values may be interpreted incorrectly.
• noMtime Set to true to omit writing mtime values for entries. Note that this prevents using other mtime-based features like tar.update or the keepNewer option with the resulting tar archive.
• mtime Set to a Date object to force a specific mtime for everything added to the archive. Overridden by noMtime.
• onWriteEntry Called with each WriteEntry or WriteEntrySync that is created in the course of writing the archive.

add(path)

Adds an entry to the archive. Returns the Pack stream.

write(path)

Adds an entry to the archive. Returns true if flushed.

end()

Finishes the archive.

class PackSync

Synchronous version of Pack.

class Unpack

A writable stream that unpacks a tar archive onto the file system.

All the normal writable stream stuff is supported. write() and end() methods, 'drain' events, etc.

Note that all directories that are created will be forced to be writable, readable, and listable by their owner, to avoid cases where a directory prevents extraction of child entries by virtue of its mode.

'close' is emitted when it's done writing stuff to the file system.

Most unpack errors will cause a warn event to be emitted. If the cwd is missing, or not a directory, then an error will be emitted.

constructor(options)

• cwd Extract files relative to the specified directory. Defaults to process.cwd(). If provided, this must exist and must be a directory.
• filter A function that gets called with (path, entry) for each entry being unpacked. Return true to unpack the entry from the archive, or false to skip it.
• newer Set to true to keep the existing file on disk if it's newer than the file in the archive.
• keep Do not overwrite existing files. In particular, if a file appears more than once in an archive, later copies will not overwrite earlier copies.
• preservePaths Allow absolute paths, paths containing .., and extracting through symbolic links. By default, / is stripped from absolute paths, .. paths are not extracted, and any file whose location would be modified by a symbolic link is not extracted.
• unlink Unlink files before creating them. Without this option, tar overwrites existing files, which preserves existing hardlinks. With this option, existing hardlinks will be broken, as will any symlink that would affect the location of an extracted file.
• strip Remove the specified number of leading path elements. Pathnames with fewer elements will be silently skipped. Note that the pathname is edited after applying the filter, but before security checks.
• umask Filter the modes of entries like process.umask().
• dmode Default mode for directories
• fmode Default mode for files
• maxMetaEntrySize The maximum size of meta entries that is supported. Defaults to 1 MB.
• preserveOwner If true, tar will set the uid and gid of extracted entries to the uid and gid fields in the archive. This defaults to true when run as root, and false otherwise. If false, then files and directories will be set with the owner and group of the user running the process. This is similar to -p in tar(1), but ACLs and other system-specific data is never unpacked in this implementation, and modes are set by default already.
• win32 True if on a windows platform. Causes behavior where filenames containing <|>? chars are converted to windows-compatible values while being unpacked.
• uid Set to a number to force ownership of all extracted files and folders, and all implicitly created directories, to be owned by the specified user id, regardless of the uid field in the archive. Cannot be used along with preserveOwner. Requires also setting a gid option.
• gid Set to a number to force ownership of all extracted files and folders, and all implicitly created directories, to be owned by the specified group id, regardless of the gid field in the archive. Cannot be used along with preserveOwner. Requires also setting a uid option.
• noMtime Set to true to omit writing mtime value for extracted entries.
• transform Provide a function that takes an entry object, and returns a stream, or any falsey value. If a stream is provided, then that stream's data will be written instead of the contents of the archive entry. If a falsey value is provided, then the entry is written to disk as normal. (To exclude items from extraction, use the filter option described above.)
• strict Treat warnings as crash-worthy errors. Default false.
• onReadEntry A function that gets called with (entry) for each entry that passes the filter.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• chmod Set to true to call fs.chmod() to ensure that the extracted file matches the entry mode. This may necessitate a call to the deprecated and thread-unsafe process.umask() method to determine the default umask value, unless a processUmask options is also provided. Otherwise tar will extract with whatever mode is provided, and let the process umask apply normally.
• processUmask Set to an explicit numeric value to avoid calling process.umask() when chmod: true is set.
• maxDepth The maximum depth of subfolders to extract into. This defaults to 1024. Anything deeper than the limit will raise a warning and skip the entry. Set to Infinity to remove the limitation.
• maxDecompressionRatio Defaults to 1000. The maximum ratio of decommpressed bytes to compressed bytes, in a compressed archive. Set to Infinity to allow explosive decompression.

class UnpackSync

Synchronous version of Unpack.

Note that using an asynchronous stream type with the transform option will cause undefined behavior in sync unpack streams. MiniPass-based streams are designed for this use case.

class tar.Parser

A writable stream that parses a tar archive stream. All the standard writable stream stuff is supported.

If the archive is gzipped, then tar will detect this and unzip it.

Emits 'entry' events with tar.ReadEntry objects, which are themselves readable streams that you can pipe wherever.

Each entry will not emit until the one before it is flushed through, so make sure to either consume the data (with on('data', ...) or .pipe(...)) or throw it away with .resume() to keep the stream flowing.

constructor(options)

Returns an event emitter that emits entry events with tar.ReadEntry objects.

The following options are supported:

• strict Treat warnings as crash-worthy errors. Default false.
• filter A function that gets called with (path, entry) for each entry being listed. Return true to emit the entry from the archive, or false to skip it.
• onReadEntry A function that gets called with (entry) for each entry that passes the filter.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")

abort(error)

Stop all parsing activities. This is called when there are zlib errors. It also emits an unrecoverable warning with the error provided.

class tar.ReadEntry extends MiniPass

A representation of an entry that is being read out of a tar archive.

It has the following fields:

• extended The extended metadata object provided to the constructor.
• globalExtended The global extended metadata object provided to the constructor.
• remain The number of bytes remaining to be written into the stream.
• blockRemain The number of 512-byte blocks remaining to be written into the stream.
• ignore Whether this entry should be ignored.
• meta True if this represents metadata about the next entry, false if it represents a filesystem object.
• All the fields from the header, extended header, and global extended header are added to the ReadEntry object. So it has path, type, size, mode, and so on.

constructor(header, extended, globalExtended)

Create a new ReadEntry object with the specified header, extended header, and global extended header values.

class tar.WriteEntry extends MiniPass

A representation of an entry that is being written from the file system into a tar archive.

Emits data for the Header, and for the Pax Extended Header if one is required, as well as any body data.

Creating a WriteEntry for a directory does not also create WriteEntry objects for all of the directory contents.

It has the following fields:

• path The path field that will be written to the archive. By default, this is also the path from the cwd to the file system object.
• portable Omit metadata that is system-specific: ctime, atime, uid, gid, uname, gname, dev, ino, and nlink. Note that mtime is still included, because this is necessary for other time-based operations. Additionally, mode is set to a "reasonable default" for most unix systems, based on a umask value of 0o22.
• myuid If supported, the uid of the user running the current process.
• myuser The env.USER string if set, or ''. Set as the entry uname field if the file's uid matches this.myuid.
• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 1 MB.
• linkCache A Map object containing the device and inode value for any file whose nlink is > 1, to identify hard links.
• statCache A Map object that caches calls lstat.
• preservePaths Allow absolute paths. By default, / is stripped from absolute paths.
• cwd The current working directory for creating the archive. Defaults to process.cwd().
• absolute The absolute path to the entry on the filesystem. By default, this is path.resolve(this.cwd, this.path), but it can be overridden explicitly.
• strict Treat warnings as crash-worthy errors. Default false.
• win32 True if on a windows platform. Causes behavior where paths replace \ with / and filenames containing the windows-compatible forms of <|>?: characters are converted to actual <|>?: characters in the archive.
• noPax Suppress pax extended headers. Note that this means that long paths and linkpaths will be truncated, and large or negative numeric values may be interpreted incorrectly.
• noMtime Set to true to omit writing mtime values for entries. Note that this prevents using other mtime-based features like tar.update or the keepNewer option with the resulting tar archive.

constructor(path, options)

path is the path of the entry as it is written in the archive.

The following options are supported:

• portable Omit metadata that is system-specific: ctime, atime, uid, gid, uname, gname, dev, ino, and nlink. Note that mtime is still included, because this is necessary for other time-based operations. Additionally, mode is set to a "reasonable default" for most unix systems, based on a umask value of 0o22.
• maxReadSize The maximum buffer size for fs.read() operations. Defaults to 1 MB.
• linkCache A Map object containing the device and inode value for any file whose nlink is > 1, to identify hard links.
• statCache A Map object that caches calls lstat.
• preservePaths Allow absolute paths. By default, / is stripped from absolute paths.
• cwd The current working directory for creating the archive. Defaults to process.cwd().
• absolute The absolute path to the entry on the filesystem. By default, this is path.resolve(this.cwd, this.path), but it can be overridden explicitly.
• strict Treat warnings as crash-worthy errors. Default false.
• win32 True if on a windows platform. Causes behavior where paths replace \ with /.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• noMtime Set to true to omit writing mtime values for entries. Note that this prevents using other mtime-based features like tar.update or the keepNewer option with the resulting tar archive.
• umask Set to restrict the modes on the entries in the archive, somewhat like how umask works on file creation. Defaults to process.umask() on unix systems, or 0o22 on Windows.

warn(message, data)

If strict, emit an error with the provided message.

Otherwise, emit a 'warn' event with the provided message and data.

class tar.WriteEntry.Sync

Synchronous version of tar.WriteEntry

class tar.WriteEntry.Tar

A version of tar.WriteEntry that gets its data from a tar.ReadEntry instead of from the filesystem.

constructor(readEntry, options)

readEntry is the entry being read out of another archive.

The following options are supported:

• portable Omit metadata that is system-specific: ctime, atime, uid, gid, uname, gname, dev, ino, and nlink. Note that mtime is still included, because this is necessary for other time-based operations. Additionally, mode is set to a "reasonable default" for most unix systems, based on a umask value of 0o22.
• preservePaths Allow absolute paths. By default, / is stripped from absolute paths.
• strict Treat warnings as crash-worthy errors. Default false.
• onwarn A function that will get called with (code, message, data) for any warnings encountered. (See "Warnings and Errors")
• noMtime Set to true to omit writing mtime values for entries. Note that this prevents using other mtime-based features like tar.update or the keepNewer option with the resulting tar archive.

class tar.Header

A class for reading and writing header blocks.

It has the following fields:

• nullBlock True if decoding a block which is entirely composed of 0x00 null bytes. (Useful because tar files are terminated by at least 2 null blocks.)
• cksumValid True if the checksum in the header is valid, false otherwise.
• needPax True if the values, as encoded, will require a Pax extended header.
• path The path of the entry.
• mode The 4 lowest-order octal digits of the file mode. That is, read/write/execute permissions for world, group, and owner, and the setuid, setgid, and sticky bits.
• uid Numeric user id of the file owner
• gid Numeric group id of the file owner
• size Size of the file in bytes
• mtime Modified time of the file
• cksum The checksum of the header. This is generated by adding all the bytes of the header block, treating the checksum field itself as all ascii space characters (that is, 0x20).
• type The human-readable name of the type of entry this represents, or the alphanumeric key if unknown.
• typeKey The alphanumeric key for the type of entry this header represents.
• linkpath The target of Link and SymbolicLink entries.
• uname Human-readable user name of the file owner
• gname Human-readable group name of the file owner
• devmaj The major portion of the device number. Always 0 for files, directories, and links.
• devmin The minor portion of the device number. Always 0 for files, directories, and links.
• atime File access time.
• ctime File change time.

constructor(data, [offset=0])

data is optional. It is either a Buffer that should be interpreted as a tar Header starting at the specified offset and continuing for 512 bytes, or a data object of keys and values to set on the header object, and eventually encode as a tar Header.

decode(block, offset)

Decode the provided buffer starting at the specified offset.

Buffer length must be greater than 512 bytes.

set(data)

Set the fields in the data object.

encode(buffer, offset)

Encode the header fields into the buffer at the specified offset.

Returns this.needPax to indicate whether a Pax Extended Header is required to properly encode the specified data.

class tar.Pax

An object representing a set of key-value pairs in an Pax extended header entry.

It has the following fields. Where the same name is used, they have the same semantics as the tar.Header field of the same name.

• global True if this represents a global extended header, or false if it is for a single entry.
• atime
• charset
• comment
• ctime
• gid
• gname
• linkpath
• mtime
• path
• size
• uid
• uname
• dev
• ino
• nlink

constructor(object, global)

Set the fields set in the object. global is a boolean that defaults to false.

encode()

Return a Buffer containing the header and body for the Pax extended header entry, or null if there is nothing to encode.

encodeBody()

Return a string representing the body of the pax extended header entry.

encodeField(fieldName)

Return a string representing the key/value encoding for the specified fieldName, or '' if the field is unset.

tar.Pax.parse(string, extended, global)

Return a new Pax object created by parsing the contents of the string provided.

If the extended object is set, then also add the fields from that object. (This is necessary because multiple metadata entries can occur in sequence.)

tar.types

A translation table for the type field in tar headers.

tar.types.name.get(code)

Get the human-readable name for a given alphanumeric code.

tar.types.code.get(name)

Get the alphanumeric code for a given human-readable name.