On Saturday, 19 September 2020 at 13:56:53 UTC, Anonymouse wrote:
On Saturday, 19 September 2020 at 13:32:07 UTC, Paul Backus
wrote:
http://dpldocs.info/experimental-docs/std.stdio.File.setvbuf.1.html
Thanks.
I don't have a clone of druntime/Phobos available to me right
now, so some follow-up questions.
It looks like full buffering _IOFBF is the default setting, but
"normal" non-Cygwin stdio certainly seems to do line buffering.
Is it getting set to line buffering _IOLBF during
initialisation of stdout? (Why then is Cygwin exempt?)
This isn't a druntime/Phobos thing, it's a libc thing. Phobos
just provides a wrapper around it.
My guess is that libc uses something like `isatty(STDOUT_FILENO)`
to determine if it should use line buffering, and that there's a
bug in Cygwin that causes isatty() to always return false. If you
want to know for sure, you can try looking through the Cygwin
source code. [1]
Is there a way to detect programmatically if I'm in an
environment where I need to manually set line buffering?
You can check the TERM environment variable [2], or you can use
the POSIX uname() function [3] to see if you're running under
Cygwin specifically. If there are any other environments where
you need to manually set line-buffering, you'll probably have to
check for those individually as well.
[1] https://cygwin.com/git/gitweb.cgi?p=newlib-cygwin.git
[2] https://cygwin.com/cygwin-ug-net/setup-env.html
[3]
https://stackoverflow.com/questions/3466166/how-to-check-if-running-in-cygwin-mac-or-linux
