bash - Use array variable in awk?

Question

A=(aaa bbb ccc)    
cat abc.txt | awk '{ print $1, ${A[$1]} }'

I want to index an array element based on the $1, but the code above is not correct in awk syntax. Could someone help?

Answer 1

You can't index a bash array using a value generated inside awk, even if you weren't using single quotes (thereby preventing bash from doing any substitution). You could pass the array in, though.

A=(aaa bbb ccc)
awk -v a="${A[*]}" 'BEGIN {split(a, A, / /)}
                     {print $1, A[$1] }' <abc.txt

Because of the split function inside awk, the elements of A may not contain spaces or newlines. If you need to do anything more interesting, set the array inside of awk.

awk 'BEGIN {a[1] = "foo bar"  # sadly, there is no way to set an array all
            a[2] = "baz"    } #   at once without abusing split() as above
           {print $1, a[$1] }' <abc.txt

(Clarification: bash substitutes variables before invoking the program whose argument you're substituting, so by the time you have $1 in awk it's far too late to ask bash to use it to substitute a particular element of A.)