How to declare an array in awk

Question

I have used awk to write a script. I am wondering how to declare an array in awk.

I have read the gnu awk manual and found nothing about declare.

i want to test if index ind is in awk array arr.

echo 'awk' | awk 'BEGIN {arr} {if ('1' in arr) arr[ind] = 1}'

i do not declare arr as an array previously and run this in awk gives me such an error.

awk: cmd. line:1: (FILENAME=- FNR=1) fatal: attempt to use scalar `arr' as an array

Answer 1

You can use the delete statement to declare an empty array:

BEGIN { delete arr[0] }
END { 
    print "len", length(arr)
    if ("1" in arr) {
        print "astonishing"
    }
}

Answer 2

Your initial arr in the BEGIN block "declares" it to be a scalar. That's what is confusing awk. Just remove that.