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Linux 2.6 - man page for deb-version (linux section 5)

deb-version(5)				      Debian				   deb-version(5)

       deb-version - Debian package version number format

       [ epoch:] upstream_version [-debian_revision ]

       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

	      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.

	      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

	      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  val-
       ues  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.

       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.

       deb-control(5), deb(5), dpkg(1)

       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				    2008-08-18				   deb-version(5)

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