deb-version(5)
NAME
deb-version - Debian package version number format
SYNOPSIS
[epoch:]upstream-version[-debian-revision]
DESCRIPTION
Version numbers as used for Debian binary and source packages consist
of three components. These are:
epoch This is a single (generally small) unsigned integer. It may be
omitted, in which case zero is assumed. If it is omitted then
the upstream-version may not contain any colons.
It is provided to allow mistakes in the version numbers of older
versions of a package, and also a package's previous version
numbering schemes, to be left behind.
upstream-version
This is the main part of the version number. It is usually the
version number of the original ("upstream") package from which
the .deb file has been made, if this is applicable. Usually
this will be in the same format as that specified by the
upstream author(s); however, it may need to be reformatted to
fit into the package management system's format and comparison
scheme.
The comparison behavior of the package management system with
respect to the upstream-version is described below. The
upstream-version portion of the version number is mandatory.
The upstream-version may contain only alphanumerics ("A-Za-
z0-9") and the characters . + - : ~ (full stop, plus, hyphen,
colon, tilde) and should start with a digit. If there is no
debian-revision then hyphens are not allowed; if there is no
epoch then colons are not allowed.
debian-revision
This part of the version number specifies the version of the
Debian package based on the upstream version. It may contain
only alphanumerics and the characters + . ~ (plus, full stop,
tilde) and is compared in the same way as the upstream-version
is.
It is optional; if it isn't present then the upstream-version
may not contain a hyphen. This format represents the case where
a piece of software was written specifically to be turned into a
Debian package, and so there is only one "debianisation" of it
and therefore no revision indication is required.
It is conventional to restart the debian-revision at '1' each
time time the upstream-version is increased.
Dpkg will break the version number apart at the last hyphen in
the string (if there is one) to determine the upstream-version
and debian-revision. The absence of a debian-revision compares
earlier than the presence of one (but note that the debian-
revision is the least significant part of the version number).
Sorting algorithm
The upstream-version and debian-revision parts are compared by the
package management system using the same algorithm:
The strings are compared from left to right.
First the initial part of each string consisting entirely of non-digit
characters is determined. These two parts (one of which may be empty)
are compared lexically. If a difference is found it is returned. The
lexical comparison is a comparison of ASCII values modified so that all
the letters sort earlier than all the non-letters and so that a tilde
sorts before anything, even the end of a part. For example, the
following parts are in sorted order: '~~', '~~a', '~', the empty part,
'a'.
Then the initial part of the remainder of each string which consists
entirely of digit characters is determined. The numerical values of
these two parts are compared, and any difference found is returned as
the result of the comparison. For these purposes an empty string
(which can only occur at the end of one or both version strings being
compared) counts as zero.
These two steps (comparing and removing initial non-digit strings and
initial digit strings) are repeated until a difference is found or both
strings are exhausted.
Note that the purpose of epochs is to allow us to leave behind mistakes
in version numbering, and to cope with situations where the version
numbering scheme changes. It is not intended to cope with version
numbers containing strings of letters which the package management
system cannot interpret (such as 'ALPHA' or 'pre-'), or with silly
orderings.
NOTES
The tilde character and its special sorting properties were introduced in dpkg 1.10 and some parts of the dpkg build scripts only gained support for it later in the 1.10.x series.
SEE ALSO
deb-control(5), deb(5), dpkg(1)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
