Spawning a process: Can I "have my cake and eat it too"?

[Steven Schveighoffer]

On 3/1/18 11:50 PM, Nick Sabalausky (Abscissa) wrote:
> I'd like to include this functionality in Scriptlike, but I don't know 
> if it's even possible:
> 
> Launch a process (spawnProcess, pipeShell, etc) so the child's 
> stdout/stderr go to the parent's stdout/stderr *without* the possibility 
> of them getting inadvertently reordered/reinterleaved when viewed on the 
> terminal, *and* still allow the parent to read the child's stdout and 
> stderr?
> 
> How could this be accomplished? Is it even possible?

You'd have to do this in the parent. You can duplicate the file 
descriptor, so that writing to either goes to the same spot, but you 
can't "fork" the file descriptor, so that writing to one goes to 2 spots.

With Phobos's std.process, you would have to allocate a buffer to store 
the data as you read from the pipe and wrote it to the terminal, it 
wouldn't be automatic.

I can think of an easy way to do it in iopipe, but it still would be 
dependent on the reader actually reading the data from the pipe. In 
other words, it wouldn't come out when the child wrote, it would only 
come out when the parent read. But this might be inherent in what you 
want, because the only way to prevent interleaving is to control it all 
from one place.

-Steve