Column number of matching string in column

Using awk:

$ string=Boo
$ echo 'Hi Boo Jiggy' | awk -v b="$string" '{for (i=1;i<=NF;i++) { if ($i == b) { print i } }}'
2

We pass your search string as an awk parameter and then loop through each field in the input. If the current field is equal to the search parameter we print it's number.

Note: this will find more than one string if they exist but will not work for substrings.