#!/bin/bash
s="alpha
beta
gamma"

#awk -v ln=1 '{print ln++  " "  $0 }'  <<< "$s"
sed -n 'x;/^$/ s/^.*$/1/;G;h;s/^/      /;s/^ *\(......\)\n/\1  /p;g;s/\n.*$//;/^9*$/ s/^/0/;s/.9*$/x&/;h;s/^.*x//;y/0123456789/1234567890/;x;s/x.*$//;G;s/\n//;h' <<< "$s"