#### streams

fd_exists () { (: <&"$1") 2>/dev/null; }

require_fd_not_exists() # usage: require_fd_not_exists fd || return 0

{ ! fd_exists "$1" || type=info die "fd $1 already exists, skipping"; }

set_fd () # usage: dest=fd dir='[<>]' src=fd [noclobber=1] set_fd

{

	inc_log_level; echo_func

	: "${dest:?}" "${dir:?}" "${src:?}"

	test ! "$noclobber" || require_fd_not_exists "$dest" || return 0

	echo_eval exec "$dest$dir&$src"

}

shadow_fd () # usage: prefix=# src=fd dir='[<>]' shadow_fd

{

	echo_minor_func

	: "${prefix:?}" "${src:?}" "${dir:?}"

	dest="$prefix$src" noclobber=1 set_fd

}