Tar

tar(1) is the tape archive utility. It creates tarballs that may or may not be compressed and/or encrypted.

There are multiple implementations:

• BusyBox implements POSIX tar(1)

• paxtar(1) which all BSDs (other than FreeBSD) use

• GNU tar(1) (or gtar(1)) is an extended implementation

• bsdtar(1), which is built on libarchive, is a further extended implementation

  • many Linux distributions will ship even further extensions by way of compilation options for libarchive

    • for example, zstd(1) support

Installation

tar(1) is POSIX and will already be installed.

If running a Linux distribution that uses gtar(1) by default, paxtar and bsdtar packages will be available.

If running a BSD distribution that uses paxtar(1) by default, gtar and bsdtar packages may be available.

If running a BSD or Linux distribution that uses bsdtar(1) by default, a gtar package may be available. Arch Linux does actually provide a paxtar package as well, but this is uncommon.

Syntax Across Implementations

POSIX tar(1) uses a bundled-argument format. All flags are bundled into the first argument.

tar cvf output.tar input-file-list

It should be immediately evident that this is a strange syntax.

The Unix format bridged the gap between this a more normal syntax.

tar -cvf output.tar input-file-list
#or
tar -c -v -f output.tar input-file-list

Each flag or cluster of flags is prefixed with -. If a flag that takes an argument is in a cluster, it must be at the end. Mandatory arguments can either be the following word (-f output.tar) or fused to the flag (-foutput.tar). A frequent tripping point: optional arguments must be fused to the flag (-g/tmp/snar.db).

The GNU format extended this with much-beloved syntactic sugar: long options.

tar --create --verbose --file output.tar input-file-list

Additionally, mandatory options can now be any of: the following word (--file output.tar), fused to the flag (--fileoutput.tar), or joined to the flag by = (--file=output.tar).

bsdtar(1) is compatible with all formats and brings additional features (automatic discovery of compression algorithms, handling of sparse files, etc.).

Per the manual of bsdtar(1): "For maximum portability, scripts that invoke tar should use the bundled-argument format above, should limit themselves to the c, t, and x modes, and the b, f, m, v, and w options."

Usage

Create a tarball.

tar --create --file archive.tar -- file1 file2 file3

Create a gzip(1)-compressed tarball.

tar --create --gzip --file archive.tar.gz -- file1 file2 file3

Compression options:

• -z and --gzip for gzip(1)

• -j and --bzip2 for bzip2(1)

• -J and --xz for xz(1)

• --auto-compress to determine compression algorithm from the file extension

  • this is a bsdtar(1) extension

• --zstd for zstd(1)

  • this is a bsdtar(1) extension that is only available on some BSD and Linux distributions

• --lzip for lzip(1), --lzma for lzma(1), --lzop for lzop(1), and -Z/--compress for compress(1)

  • don't use these

Create a gzip(1)-compressed, gpg(1)-encrypted tarball.

tar --compress --gzip -- file1 file2 | gpg --symmetric --output archive.tar.gz.gpg

Extract the contents of a tarball.

tar --extract --file archive.tar

Extract the contents of a gzip(1)-compressed tarball.

tar --extract --gzip --file archive.tar.gz

Extract the contents of a gzip(1)-compressed, gpg(1)-encrypted tarball.

gpg --decrypt archive.tar.gz.gpg | tar --extract --gzip

List the contents of a tarball.

tar --list --file archive.tar

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