How to handle variables inside scripts

[MartinHelmut]

As seen in https://github.com/krieselreihe/litr/wiki/Setup#example variables can be used with ${...} inside scripts

Open questions

• What syntax should be used / is ${...} really a good choice?
• Is there a way to have this as environment variables? Should this even?
• How is the variable context defined? E.g. always string, no matter what? Some kind of parsing?

[MartinHelmut]

Using environment variables

Cons

• Not out of the box cross OS
• Potential collision with existing variables, otherwise a prefix needs to be defined as NPM does (ref)
• Does not work together with parameter functions

Pros

• Can be used anywhere an environment variable is used

Using the ${} syntax

Cons

• A syntax the user needs to learn
• Can only be used inside the configuration scripts, not in files

Pros

• Cross OS
• Parameter functions work
• No pollution of the environment

[MartinHelmut]

Issue

The ${} syntax will conflict with regular bash syntax, e.g. echo "${something}", making parsing harder. Also, it will not be possible to guess the user intend, if this should be an environment variable or a Litr variable. A different syntax is needed.

Solution

Use %{} syntax. This does not interfere with existing Bash syntax, can be echoed in or outside a string, but is still familiar inside the general topic of string interpolation.

To escape this sequence use \%{}.