If it is streamed data you will probably get your chunks at byte boundary (as this is the level at which your interface transfers the data) and unless the protocol specifies something that is not aligned at byte boundaries, you can safely assume binary.

BUT If the data is streamed in, you can’t safely use binary pattern matching at all but need to use a different mean of parsing/deserializing the incomming data.

What happens if your current chunk is "tru"? This does not match "true", but might after the next chunk has been received.

@DimWell Just for the record, what you were trying to do is possible, you just need to use the suffix ‘bits-’ or ‘bytes-’…

<<x::bits-size(16), _::binary>> = "true"
inspect(x) # "tr"

<<x::bytes-size(2), _::binary>> = "true"
inspect(x) # "tr"

;D

If I understood the problem properly, you want to match the beginning of the input string? In this case, it is easy:

def match_bitstring("true" <> _rest), do: IO.puts("true")
def match_bitstring("false" <> _rest), do: IO.puts("false")