redirfd

const (
	Read           RedirectMode = iota // open file for reading
	Write                              // open file for writing, truncating if it exists
	Update                             // open file for read & write
	Append                             // open file for append, create if it does not exist
	AppendExisting                     // open file for append, do not create if it does not already exist
	WriteNew                           // open file for writing, creating it, failing if it already exists
)