Exploring terminfo

[Eryk Sun]

On 1/16/21, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> On 17/01/21 12:40 pm, Chris Angelico wrote:
>> This is true. However, at some point, the boundary is crossed from
>> Python into the C library. Something, at that point, knows. It's very
>> common to have a flush option available, so it should be used.
>
> I'm wondering whether the problem in this particular case stems
> from trying to use parts of curses without initialising it
> properly. I expect that initialising curses would put stdout
> into some kind of unbuffered mode, and the rest of it assumes
> that this has been done.

The buffering mode cannot be changed for an in-use stream: "setvbuf()
... may be used only after opening a stream and before any other
operations have been performed on it". So it would have to open a new
stream, which can only be done legitimately by device or file name via
C freopen(). Code that overwrites the FILE record (e.g. *stdout =
*stream) is not legitimate and cross-platform.

You can force the interpreter to change stdout to unbuffered mode at
startup via `-u` or the PYTHONUNBUFFERED environment variable. In
Linux, there's also the `stdbuf` command (e.g. stdbuf -o0 python
....), which uses an LD_PRELOAD hook to inject a shared library that
calls setvbuf() at process startup. There's no analog to that in
Windows for various reasons.