Search position of substring inside a string

[ale5000-git]

With Bash I can get the position by using : echo '012my_substring345' | grep -F -o -b -- 'my_substring'

Is there a way to get it on busybox? (possibly sticking to POSIX code)

[avih]

# $1: haystack  $2: needle
printpos() {
    [ -z "${2-}" ] && echo 0 ||
    { set -- "$1" "${1%%"$2"*}" && [ "$1" != "$2" ] && echo ${#2}; }
}

This prints 0-based pos of $2 in $1, or error if $2 is not a substring of $1.

[ale5000-git]

Works perfectly, thanks.