I have a working redirecting context on Ubuntu (no tests run yet).
But I guess I need to think a little more about the blocking issue.
What we're doing here is, fork a child (which runs the command) and connect
us to the child through at most three pipes. A stdin pipe, a stdout pipe,
and an error pipe. We write to the stdin pipe, which the child then reads,
and the child writes to both the stdout and the error pipe, which we than
will read back in.
Now pipes are something that the OS provides and it does some buffering for
us: you can write stuff to a pipe, before the child consumes it. But it's
just a small buffer, 4K or 64K. After that the pipe may block (or break,
which I may have experienced)
So if we're eager to send stuff through the stdin pipe for the child to use
it, and the child is slow, or, worse, doesn't even expect anything on
stdin, the pipe blocks and we're stalled. In the meantime we could do a
little reading on the output or error pipe, because the child may be slow,
because it itself has already filled up, say, its output pipe and reading
that would be a relief (break the stall), but I'm not sure how to actually
do this.
When do we write, when read? Which pipes? How large pipe read/write blocks
do we use? Do we sleep a little bit in between?
I also need to figure out how to do non-blocking reads.
We don't yet have ADDRESS WITH tests for a real Unix redirecting command
context yet, have we?
On Wed, Apr 4, 2018 at 4:04 PM, Erich Steinböck <erich.steinbo...@gmail.com>
wrote:
> From the description in https://blog.uxul.de/e?e=mt-160 (very bottom) it
> seems "trivial" to do.
> Not a Linux guru at all, but I'd give it a try if no one else volunteers.
>
> The blog also contains a discussion of an interesting quirk with fork(),
> which is why the sample code uses POSIX spawn to execute the command.
> POSIX spawn seems to be available on all the platforms ooRexx supports.
> Not on Android though.
>
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