Chapter 5. Control files and their fields

34

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 in 

creased.

The package management system 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).

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.

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 (the author of this

manual has heard of a package whose versions went

1.1

,

1.2

,

1.3

,

1

,

2.1

,

2.2

,

2

and so

forth).

5.6.13

Description

In a source or binary control file, the

Description

field contains a description of the binary

package, consisting of two parts, the synopsis or the short description, and the long descrip 

tion. The field's format is as follows:

Description: 

The lines in the extended description can have these formats:

  Those starting with a single space are part of a paragraph. Successive lines of this form

will be word wrapped when displayed. The leading space will usually be stripped off.