45

Chapter 7

Declaring relationships between

packages

7.1 Syntax of relationship fields

These fields all have a uniform syntax. They are a list of package names separated by commas.

In the

Depends

,

Recommends

,

Suggests

,

Pre Depends

,

Build Depends

and

Build Depends Indep

control file fields of the package, which declare dependencies

on other packages, the package names listed may also include lists of alternative package

names, separated by vertical bar (pipe) symbols

|

. In such a case, if any one of the alternative

packages is installed, that part of the dependency is considered to be satisfied.

All of the fields except for

Provides

may restrict their applicability to particular versions of

each named package. This is done in parentheses after each individual package name; the

parentheses should contain a relation from the list below followed by a version number, in the

format described in `

Version

' on page

33

.

The relations allowed are

<<

,

<=

,

=

,

>=

and

>>

for strictly earlier, earlier or equal, exactly

equal, later or equal and strictly later, respectively. The deprecated forms

<

and

>

were used to

mean earlier/later or equal, rather than strictly earlier/later, so they should not appear in new

packages (though

dpkg

still supports them).

Whitespace may appear at any point in the version specification subject to the rules in `Syntax

of control files' on page

27

, and must appear where it's necessary to disambiguate; it is not

otherwise significant. For consistency and in case of future changes to

dpkg

it is recommended

that a single space be used after a version relationship and before a version number; it is also

conventional to put a single space after each comma, on either side of each vertical bar, and

before each open parenthesis.

For example, a list of dependencies might appear as:

Package: mutt

Version: 1.3.17 1

Depends: libc6 (>= 2.2.1), exim | mail transport agent