bash: Variable substitution - If variable is unset, set variable to word.

indigowinged

Take into account the main readme for this section. README first.

Syntax is:
${name=word}

if the variable $name is unset, then set variable to word.

Here Brazil is set, has a value of SugarCane, hence no Brazil stays as SugarCane.

$ Brazil=SugarCane
$ Amazon=${Brazil=NoDeforestation}
$ echo $Amazon
SugarCane

Now change Brazil to Brazil1 and try again.

$ Amazon=${Brazil1=NoDeforestation}
$ echo $Amazon
NoDeforestation
$ echo $Brazil1
NoDeforestation