Chapter 9. The Operating System

75

9.9 Environment variables

A program must not depend on environment variables to get reasonable defaults. (That's

because these environment variables would have to be set in a system wide configuration file

like

/etc/profile

, which is not supported by all shells.)

If a program usually depends on environment variables for its configuration, the program

should be changed to fall back to a reasonable default configuration if these environment vari 

ables are not present. If this cannot be done easily (e.g., if the source code of a non free program

is not available), the program must be replaced by a small  wrapper  shell script which sets

the environment variables if they are not already defined, and calls the original program.

Here is an example of a wrapper script for this purpose:

#!/bin/sh

BAR=${BAR: /var/lib/fubar}

export BAR

exec /usr/lib/foo/foo "$@"

Furthermore, as

/etc/profile

is a configuration file of the

base files

package, other

packages must not put any environment variables or other commands into that file.

9.10 Registering Documents using doc base

The

doc base

package implements a flexible mechanism for handling and presenting doc 

umentation. The recommended practice is for every Debian package that provides online

documentation (other than just manual pages) to register these documents with

doc base

by installing a

doc base

control file via the

install docs

script at installation time and

de register the manuals again when the package is removed.

Please refer to the documentation that comes with the

doc base

package for information and

details.