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deb-version(5) Debian 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 charac-
ters . + - : ~ (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 "debiani-
sation" 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 sys-
tem 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 number-
ing, 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 man-
agement system cannot interpret (such as 'ALPHA' or 'pre-'), or with silly orderings.
CAVEATS
The tilde character and its special sorting properties were introduced in dpkg, version
1.10 and some parts of dpkg-dev only gained support for it later in the 1.10.x series.
SEE ALSO
deb-control(5), deb(5), dpkg(1)
AUTHORS
Copyright (C) 1996,1997,1998 Ian Jackson and Christian Schwarz
Copyright (C) 2007 Frank Lichtenheld
This is free software; see the GNU General Public Licence version 2 or later for copying
conditions. There is NO WARRANTY.
Debian Project 2007-10-06 deb-version(5)
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