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
           “debianization” of it and therefore no revision indication is required.

           It is conventional to restart the debian-revision at ‘1’ each 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)