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  num-
	      bering 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-ver-
	      sion 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 exam-
       ple, 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  sys-
       tem 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)

Debian Project							    2011-08-14							    deb-version(5)