I'm really fond of "null coalescing", where you can set a variable to the first "non-null" value in a list of things. Many languages support this, for example:

C#:

String myStr = string1 ?? string2 ?? "default"; 

JavaScript:

var myStr = string1 || string2 || "default"; 

...etc. I'm just curious if this can be done in Bash to set a variable?

pseudo:

MY_STR=$ENV{VAR_NAME}??$ANOTHER_VAR??"default";