Run Goal and once/1 while capturing all output to all streams
(current_output
, user_output
and user_error
) in the string
Output. Options processed:
- capture(ListOfStreams)
- List of streams to capture. Default is
[]
, causing the
predicate to call with_output_to/2. The only admissible
list elements are the alias names for the Prolog standard
streams. As current_output
is always captured, the only
two values are user_output
and user_error
- color(Boolean)
- When
true
, pretend the output is a terminal, causing messages
to use ANSI term escape sequences for color.
For example, the following captures an error message. Note that
we must catch and print the message inside Goal. If we do not do
so the exception of Goal is simply propagated into the environment
without binding Output.
?- with_output_to(string(Out),
catch(A is log(-1), E, print_message(error, E)),
[capture([user_error]), color(true)]).
Out = "\u001B[1;31mERROR: is/2: Arithmetic: \c
evaluation error: `undefined'\n\u001B[0m",
E = error(evaluation_error(undefined), context(system:(is)/2, _)).