is it possible to intercept the  STDOUT or STDERR and capture the output into a variable ?


some pseudocode to explain what I mean

string[] output_buffer;
stdout.capture_to(output_buffer);

writeln("test 1"); # not printed
writeln("test 2"); # not printed

stdout.release(output_buffer);

writeln("test 3"); # printed
writeln(output_buffer); # prints '["test 1","test 2"]'

On Wednesday, 1 February 2017 at 01:08:19 UTC, Emil wrote:
> is it possible to intercept the  STDOUT or STDERR and capture the output into a variable ?
>
>
> some pseudocode to explain what I mean
>
> string[] output_buffer;
> stdout.capture_to(output_buffer);
>
> writeln("test 1"); # not printed
> writeln("test 2"); # not printed
>
> stdout.release(output_buffer);
>
> writeln("test 3"); # printed
> writeln(output_buffer); # prints '["test 1","test 2"]'

No.
Please keep in mind, that in Linux, for example, stdout is a file ...
writeln() interacts with OS API, which, of course, has nothing to do with internal data structures of your application.
What you could probably do is replace writeln() with a custom logger. In your logger implementation you can add such functionality.

On Wednesday, 1 February 2017 at 01:08:19 UTC, Emil wrote:
> is it possible to intercept the  STDOUT or STDERR and capture the output into a variable ?
>
>
> some pseudocode to explain what I mean
>
> string[] output_buffer;
> stdout.capture_to(output_buffer);
>
> writeln("test 1"); # not printed
> writeln("test 2"); # not printed
>
> stdout.release(output_buffer);
>
> writeln("test 3"); # printed
> writeln(output_buffer); # prints '["test 1","test 2"]'

If you *had* to, you should be able to hack it by reopening the file descriptors for standard output or error (at least on *nix), but is there a specific reason you want to do this, or do you just want formatted output to a variable?

On Wednesday, 1 February 2017 at 14:38:18 UTC, angel wrote:
> On Wednesday, 1 February 2017 at 01:08:19 UTC, Emil wrote:
>> is it possible to intercept the  STDOUT or STDERR and capture the output into a variable ?
.....
>> writeln(output_buffer); # prints '["test 1","test 2"]'
>
> No.
> Please keep in mind, that in Linux, for example, stdout is a file ...
> writeln() interacts with OS API, which, of course, has nothing to do with internal data structures of your application.
> What you could probably do is replace writeln() with a custom logger. In your logger implementation you can add such functionality.

Thank you.