Input/output of DEC-10 Prolog (not in ISO)

This section describes the built-in predicates for file manipulation inherited from DEC-10 Prolog. These predicates refer to streams by file names. The atom user is a reference to both the standard input and standard output streams.

• see(FileName): Makes the file FileName the current input stream. It is equivalent to:

        open(FileName,read,Stream),set_input(Stream).
  

• seeing(File): The current input stream is named FileName. It is equivalent to:

        current_input(Stream),stream_property(Stream,file_name(FileName)).
  

• seen: Closes the current input stream. It is equivalent to:

        current_input(Stream),close(Stream).
  

• tell(FileName): Makes the file FileName the current output stream. It is equivalent to:

        open(FileName,write,Stream),set_output(Stream).
  

• telling(FileName): The current output stream is named FileName. It is equivalent to:

        current_output(Stream),
        stream_property(Stream,file_name(FileName).
  

• told: Closes the current output stream. It is equivalent to:

        current_output(Stream),close(Stream).
  

• get(Code): Code is the next printable byte code in the current input stream.

• get0(Code): Code is the next byte code in the current input stream.

• put(Code): Output the character to the current output stream, whose code is Code.

• tab(N): Outputs N spaces to the current output stream.

• exists(F): Succeeds if the file F exists.