Initialize environment variables

This document describes the mechanism to initialize an environment variable to a given value the first time this variable is changed.

This is especially useful for variable like MANPATH that requires a leading or finishing colon character in addition to the specific paths defined to still be able to query the system man pages.

Design choices:

• If environment variable is changed and currently not defined, set it to the defined initial value prior applying the change

• When removing value to path-like environment variable, if after the removal it equals the initial value without specific reference counter, unset the environment variable

This mechanism applies to all path-like environment variable management modulefile commands and module sub-commands:

• append-path

• prepend-path

• remove-path

init_envvars configuration option

New configuration option init_envvars is made to define the initial value of the environment variables.

• Items are separated by colon character

• Each item has the following syntax: VARNAME=initial_value