o bar baz; do eval echo \${$foo:?} one bash: bar: parameter null or not set bash: baz: parameter null or not set
== NOTE ==
The colon (:) in t... pt. Omitting message produces the default message parameter null or not set.
Purpose:
Catching errors tha... hat the GNU version of basename takes an optional parameter. This handy for specifying a filename "extension"... bash").
However, buried in there is a section on Parameter Substitution which tells us that $foo is really a
