On Friday, 5 June 2020 at 20:11:16 UTC, aberba wrote:
Didn't come to mind to lookup from terminal docs. Thought it was a Dlang/OS problem.
Yeah, the OS by itself rarely buffers output like this, but both the C library (on which std.stdio is built) and my Terminal object do (they do separately btw, which is why I suggest you avoid mixing together terminal.writeln and regular stdout.writeln, since they can intermix unpredictably as they flush at different calls).
The C one tends to auto-flush on newline, unless it is piped to another program... which confuses poor users on IDEs, since from the program's perspective, the IDE console is another program! So your output can be delayed differently there vs direct to the user's screen. (My terminal.d will actually throw an exception if you try to use it in such an environment. You need to check Terminal.stdoutIsTerminal() if you want to handle that case differently. This is another decision I semi-regret and might change in the future, since a lot of things do work fine in that environment, you just can't move the cursor around in it.)
Anyway the point is just that output functions often pretend to succeed while actually just buffering it internally. Unless the docs say otherwise when using one of these, there's no guarantee it will actually display until you call the library's flush function (in std.stdio btw it is `stdout.flush();`, in C it is `fflush(stdio);`) or close the file.
