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Title: Plain Text Archives (ptar) README
Author: Jordan Vaughan
Format: Markdown with MultiMarkdown metadata extensions
Copyright: Written in 2013 by Jordan Vaughan. To the extent possible under law, Jordan Vaughan has waived all copyright and related or neighboring rights to this publication. You can copy, modify, distribute and perform this publication, even for commercial purposes, all without asking permission. Please see http://creativecommons.org/publicdomain/zero/1.0/ for more information.
This is a tool that creates, examines, and extracts files from plain text archives that are simliar to traditional
tar(1) archives but are more human-readable.
“Why did you make this?”
I wanted to try to make a simple yet extensible file archive format using only plain text. Thanks to its ubiquity and entrenchment in computing, plain text files are the best long-term digital archival format. The most widely used UNIX archive format is
tar(1)’s, so I tried to make something equivalent to
tar(1) but with plain text metadata. Plain text archives (ptars) offer nearly equivalent functionality (and sometimes space savings) but with the promise of better longevity.
tar(1) good enough?”
Yes, it is. But using
ptar will increase your data’s longevity (archival quality) because the metadata is easier to examine and interpret.
“Why did you reinvent the wheel?”
Because I wanted to. Seriously, though,
ptar adds value: metadata that can be easily grokked in a plain text editor.
Get the source. Open a terminal and navigate to the directory containing the source. Run
make to build
ptar, like so:
ptar will be built in the directory containing the source code. To install it, run
% make install
ptar will be installed in
/usr/bin and its owner and group will be
root by default. To change the installation directory, set the
BINDIR make variable. You can change
ptar’s owner and group via
INSTALL_GROUP make variables. For example,
% make BINDIR=$HOME/bin INSTALL_USER=yourstruly INSTALL_GROUP=yourstruly install
$HOME/bin. Its owner and group will both be
Alternatively, there’s a simpler installation script,
install.sh, for systems lacking
make(1). To run it, execute this:
% ./install.sh DESTDIR
DESTDIR is the directory where the programs will be installed. You need to define the
CC environment variable as the name or path of your system’s C compiler. For example, if your system uses GCC, then you could do this:
% CC=gcc ./install.sh DESTDIR
You’ll have to manually set the
ptar installed binary’s username and group if you use
After installation, invoke
ptar with the
-help option for a detailed help message, like so:
% ptar --help
See FORMAT.md for a detailed description of the
ptar format and examples. Consider including this file in your ptars so that people examining them will have a guide to understanding them (thus increasing your ptars’ long-term archival value).
ptarmetadata is readable with any plain text editor and is easy for those versed in UNIX lingo to understand;
tar(1)metadata is not. This is
ptar’s greatest strength.
ptarmetadata values are theoretically unbounded, whereas
tar(1)metadata is limited in most cases.
ptarpreserves modification times by default, whereas many
ptarcommand has fewer options than some implementations of
tar(1), such as GNU tar. However, the most commmon operations are available: create, list, and extract.
Although ptars require additional space per piece of metadata to store key names (tars don’t tag metadata with key names), each tar entry’s metadata must occupy a multiple of 512 bytes. Therefore, some ptars will use less space than their equivalent tars. However, the reverse is true: Some tars will use less space than their equivalent ptars. They seem to be about the same on average. They compress almost equally well.
ptar runs a little slower than most implementations of
tar(1) because it has to do text processing for metadata. However, the slowdown isn’t tremendous. Try it for yourself.
Copyright? Hah! Here’s my “copyright”:
This program was written in 2013. See AUTHORS for a list of authors.
To the extent possible under law, the author(s) have dedicated all copyright and related and neighboring rights to this software to the public domain worldwide. This software is distributed without any warranty.
You should have received a copy of the CC0 Public Domain Dedication along with this software. If not, see http://creativecommons.org/publicdomain/zero/1.0/.
See COPYING for the CC0 Public Domain Dedication text.