Reading into the output of a long running shellExecute

[helxi]

On Saturday, 10 November 2018 at 15:54:07 UTC, JN wrote:
> On Saturday, 10 November 2018 at 15:05:38 UTC, helxi wrote:
>> Hi. I have not done any multi-threaded programming before. 
>> What I basically want is to read into the output of a long 
>> shellExecute function each second.
>>
>> In details, I am calling shellExecute("pkexec dd 
>> if=/path/to/file of=/dev/sdx status=progress && sync");
>> It's a long running process and dd command prints how many 
>> bytes it has written in stdout continuously. I want to read 
>> and parse this output each second. How should I proceed?
>
> shellExecute won't work, because it waits for the process to 
> end before moving on.
>
> I believe https://dlang.org/phobos/std_process.html#pipeProcess 
> should do what you want. It returns a ProcessPipes object which 
> has stdout, from which you should be able to read.

Okay I looked it up but now I have another question

      1	import std.process;
      2	import std.stdio;
      3	import std.range;
      4	import std.string;
      5	
      6	//    pkexec dd 
if=/run/media/user1101/portable_drive/software/os/manjaro-kde-18.0-stable-x86_64.iso of=/dev/sdd bs=4M status=progress 2>&1 && sync
      7	
      8	void main() {
      9	    auto pipe = pipeShell("bash", Redirect.stdout | 
Redirect.stderr | Redirect.stdin);
     10	    pipe.stdin.writeln(
     11	        "pkexec dd 
if=/run/media/user1101/portable_drive/software/os/manjaro-kde-18.0-stable-x86_64.iso of=/dev/sdd bs=4M status=progress 2>&1 && sync"
     12	    );
     13	    pipe.stdin.flush();
     14	    pipe.stdin.close();
     15	
     16	    foreach (line; pipe.stdout.byLineCopy)
     17	        foreach (word; line.split)
     18	            writeln(word);
     19	}

What I want is to instantly print whatever dd prints to the 
stdout. (I made dd to redirect output to stdout with 2>&1 
already). But the problem is, the pipe waits until dd finishes 
writing to stdout. How can I make the pipe not wait for dd to 
finish?

}