util-linux/bash-completion/blkdiscard

_blkdiscard_module()
{
	local cur prev OPTS
	COMPREPLY=()
	cur="${COMP_WORDS[COMP_CWORD]}"
	prev="${COMP_WORDS[COMP_CWORD-1]}"
	case $prev in
		'-o'|'--offset'|'-l'|'--length')
			COMPREPLY=( $(compgen -W "num" -- $cur) )
			return 0
			;;
		'-h'|'--help'|'-V'|'--version')
			return 0
			;;
	esac
	case $cur in
		-*)
			OPTS="--offset --length --secure --verbose --help --version"
			COMPREPLY=( $(compgen -W "${OPTS[*]}" -- $cur) )
			return 0
			;;
	esac
	local DEVS
	DEVS=''; while read dev; do DEVS+="$dev " ; done < <(lsblk -pnro name)
	COMPREPLY=( $(compgen -W "$DEVS" -- $cur) )
	return 0
}
complete -F _blkdiscard_module blkdiscard