#!/bin/bash

# 次のような逐次的な文字列を出力する:
#   a b c ... z
#   aa ab ac ... az
#   za zb zc ... zz
#   aaa aab aac ... aaz
#   zza zzb zzc ... zzz

atoz="{a..z}"

while true; do
  for str in $(eval echo ${atoz}); do
    echo ${str}
  done
  atoz="${atoz}{a..z}"
done
