source: vendor/grep/2.12/tests/reversed-range-endpoints

#!/bin/sh
# Ensure that an invalid range like [b-a] evokes exit status of 2.
. "${srcdir=.}/init.sh"; path_prepend_ ../src

fail=0

printf 'Invalid range end\n' > exp
for prog in grep egrep 'grep -E'; do
  $prog '[b-a]' < /dev/null > out 2>&1
  # exit status must be 2, not 1
  test $? = 2 || fail=1

  # Remove "$prog: " prefix from actual output.
  sed 's/^[grep]*: //' out > k && mv k out

  compare exp out || fail=1
done

Exit $fail