SWI-Prolog 10.0.2 Reference Manual: Section 4.38

## 4.38 Creating a Protocol of the User Interaction

SWI-Prolog offers the possibility to log the interaction with the user on a file.162A similar facility was added to Edinburgh C-Prolog by Wouter Jansweijer. All Prolog interaction, including warnings and tracer output, are written to the protocol file.

protocol(+File)
  Start protocolling on file File. If there is already a protocol file open, then close it first. If File exists it is truncated.
protocola(+File)
  Equivalent to protocol/1, but does not truncate the File if it exists.
noprotocol
  Stop making a protocol of the user interaction. Pending output is flushed on the file.
protocolling(-File)
  True if a protocol was started with protocol/1 or protocola/1 and unifies File with the current protocol output file.