Opens a named pipe in given path, creates the named pipe -file if needed

open_named_pipe.rb

    # Open one end of named pipe
    # @argument pipe_path - path to fifo
    # @argument flag - [r, w, w+, ...
    # @argument wait_on_str - continue if can read]
    # @returns named_pipe -handle
    def named_pipe( pipe_path, flag, wait_on_str=nil )
      if File.exists? pipe_path
        raise "bad #{pipe_path}" unless File.pipe? pipe_path
      end
      pipe_handle = File.mkfifo pipe_path
      pipe_handle.open(flag) # ?
                 
      ### not sure this is right, but this is the simpler strategy above ###  
        
      if wait_on_str
        msg = pipe_handle.gets # blocks until content
        unless msg&.include? wait_on_str
          error = "no handshake #{msg} in #{pipe_path} - FAIL"
          p_dbg error, self
          raise error
        end
      end 
      
      pipe_handle
      
    end

    # Reads from a named pipe
    # @agument timeout_secs_int - timeout for waiting on something to read
    # @argument readlen_bytes - number of bytes to read
    # @return nil if nothing to read
    def read_bytes_nonblocking( pipe_handle_io, timeout_secs_int=0, readlen_bytes=2 )
      msg = nil
      rwe = IO.select([pipe_handle_io], [], [], timeout_secs_int)
      msg = rwe[0][0].read(readlen_bytes) unless rwe == nil
      msg.strip if msg != nil
    end