BootstrappingTar

How to get a tar if you don't already have one.

The libarchive distribution builds bsdtar, which is a full-featured command-line tar program.

The source code is distributed in two forms:

• as a tar archive that has been compressed with gzip
• as a zip archive

If you don't already have software that can extract such archives, this may be problematic. The remainder of this article explains one way around this chicken-and-egg problem.

You can use very simple tools to unpack the libarchive distribution in two steps:

1. uncompress the distribution file to obtain an uncompressed tar archive
2. untar the result to obtain the individual files

Once you have the unpacked files, you can then follow the BuildInstructions to build bsdtar.

Gunzip

For ease of downloading, the libarchive distribution is compressed. To use the "untar" program below, you'll need to first uncompress the libarchive distribution to obtain an uncompressed tar archive. This can be done by the gunzip program, or by the gzip program with the `-d` (decompress) option. Precompiled versions are available for most platforms; you can check http://www.gzip.org/ for details.

Of course, you can also download the libarchive distribution onto a system that has gzip, decompress it there, then copy the uncompressed libarchive-XX.YY.ZZ.tar onto the target system and untar it.

Untar

I've created an extremely minimal C program called "untar" that knows just enough about the tar format to extract a simple uncompressed tar archive. It does not rely on libarchive, so it can be used to unpack the libarchive distribution after you decompress it.

You can obtain the source for untar from:

https://raw.github.com/libarchive/libarchive/master/contrib/untar.c

The "untar" program is written using only Standard ISO C89 (with one exception explained below). As such, it should compile easily on any platform with a C compiler:

$ cc -o untar untar.c

That one exception is the `mkdir()` function for creating a directory. Unfortunately, ISO C does not provide a standard function for creating a directory, so I've used the POSIX.1 standard `mkdir()` function. Most platforms have `mkdir()`, though you may need to adjust the headers somewhat. If your platform does not have `mkdir()`, you may need to edit the `create_dir` function to create a directory in some other way.

The untar.c source code can also be used as an extremely small implementation of a tar unpacker for use in very space-constrained applications. The source is in the public domain, please feel free to use it as you see fit.

(Note: There is another `untar.c` file in the libarchive distribution that does use libarchive. That example is more full-featured but obviously requires that libarchive itself be compiled and available.)