• Nick Sabalausky (Abscissa) (8/8) Mar 01 2018 I'd like to include this functionality in Scriptlike, but I don't know
• Adam D. Ruppe (9/9) Mar 01 2018 I would suggest redirecting the child to the parent pipe, but
• Vladimir Panteleev (6/11) Mar 01 2018 I think it's possible on Linux.
• Steven Schveighoffer (14/24) Mar 02 2018 You'd have to do this in the parent. You can duplicate the file
• Steven Schveighoffer (6/12) Mar 02 2018 Hm.. you could potentially do this via an intermediary process that does...

"Nick Sabalausky (Abscissa)" <SeeWebsiteToContactMe semitwist.com> writes:

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?

Adam D. Ruppe <destructionator gmail.com> writes:

I would suggest redirecting the child to the parent pipe, but 
then having the parent write the data back out to its own 
stdout/err.

It'd be a bit tricky with just Phobos' file though because it 
doesn't make it easy to wait for or be notified about input on 
it, but the underlying OS apis make this reasonably simple 
(WaitForMultipleObjects or select) if you're willing to write a 
bit more code to do it yourself or at least pull the underlying 
handles out of the Phobos file.

Vladimir Panteleev <thecybershadow.lists gmail.com> writes:

On Friday, 2 March 2018 at 04:50:06 UTC, Nick Sabalausky 
(Abscissa) wrote:
 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?

I think it's possible on Linux.
1. Disable buffering on the pipe (see stdbuf etc.)
2. Fake output type to fool isatty (e.g. script -c 'child_program 
args...' /dev/null)

Steven Schveighoffer <schveiguy yahoo.com> writes:

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

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 3/2/18 9:23 AM, Steven Schveighoffer wrote:
 On 3/1/18 11:50 PM, Nick Sabalausky (Abscissa) wrote:
 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.

Hm.. you could potentially do this via an intermediary process that does 
the copying. Then you could avoid writing the buffering code in your 
parent or child.

i.e. something like the Unix tee command.

-Steve