Is there a way of finding index by content without loop in bash

Question

I am wondering if there is a simple solution (one line command of sed or awk) of finding index by content in bash. For example, array=(a b c d e), given a target element "d", how can I get its corresponding array index of 3 without looping through the array and comparing each element with the target?

Answer 1

Try this with GNU grep:

array=(a b c d e)
declare -p array | grep -Po '\[\K[^\]](?=\]="d")'

or with sed:

array=(a b c d e)
declare -p array | sed 's/.*\[\([^\[]\)\]\+="d".*/\1/'

Output with grep and sed:

3

---

With a variable:

array=(a b c d e)
target="d"
index="$(declare -p array | grep -Po '\[\K[^\]](?=\]="'"$target"'")')"
echo "$index"