Easiest way to check for an index or a key in an array?

Question

Using:

set -o nounset

1. Having an indexed array like:

   myArray=( "red" "black" "blue" )
            
   
   
           

Answer 1

From man bash, conditional expressions:

-v varname
              True if the shell variable varname is set (has been assigned a value).

example:

declare -A foo
foo[bar]="this is bar"
foo[baz]=""
if [[ -v "foo[bar]" ]] ; then
  echo "foo[bar] is set"
fi
if [[ -v "foo[baz]" ]] ; then
  echo "foo[baz] is set"
fi
if [[ -v "foo[quux]" ]] ; then
  echo "foo[quux] is set"
fi

This will show that both foo[bar] and foo[baz] are set (even though the latter is set to an empty value) and foo[quux] is not.