#compdef tac gtac

local variant

_pick_variant -r variant gnu='Free Soft' unix --version

# NetBSD (at least) has its own bare-bones version of this tool
[[ $variant == gnu ]] || {
  _default
  return
}

_arguments -s -S : \
  '(: -)--help[display help information]' \
  '(: -)--version[display version information]' \
  '(-b --before)'{-b,--before}'[attach separator before instead of after]' \
  '(-r --regex)'{-r,--regex}'[treat separator as regular expression (with -s)]' \
  '(-s --separator)'{-s+,--separator=}'[use specified separator instead of newline]:separator' \
  '*: :_files'