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	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_revi-
	      sion 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 fol-
       lowing 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 num-
       bers  containing strings of letters which the package management 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			  2008-08-18			deb-version(5)