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digitalmars.D.learn - How to read live output from another process ?

reply Vinod K Chandran <kcvinu82 gmail.com> writes:
Hi all,
I am trying to create a program which burns time codes to a 
video. I am using ffmpeg for this. So far, I can successfully 
start ffmpeg in another thread and stop it when I need. But I 
can't read the live outputs from ffmpeg. This is my code.
```d
void onBtnBurnClick(Control c, EventArgs e) {
	if (!burnStarted) {
		burnStarted = true;
		btnBurn.text = "Stop Burning";
		auto ffCmd = makeFFMPEGCommand(selVideo);
           // ffPipe is a global ProcessPipes
		auto tsk = task!runFFMPEG(ffCmd, &ffPipe, frm.handle);
		tsk.executeInNewThread();
	} else {
		ffPipe.stdin.writeln("q");
		ffPipe.stdin.close();
		btnBurn.text = "Burn Time Code";
	}
}
```
This is a button's click event.
Jun 23 2023
next sibling parent Vinod K Chandran <kcvinu82 gmail.com> writes:
On Friday, 23 June 2023 at 23:37:29 UTC, Vinod K Chandran wrote:

 Hi all,


Hi, I found the solution by myself. We can use Pipe struct for 
this job.
Here is the code looks like. This is for future readers.

```d
void onBtnBurnClick(Control c, EventArgs e) { // A button click 
event handler
	if (!jobStarted) {
		jobStarted = true;
		btnBurn.text = "Stop the job";
		string cmd = makeCommand();
		ff = spawn(&runInAnotherThread, cmd); // ff is global var
	} else {
		ff.send(-1); // Send a signal to stop the job
		btnBurn.text = "Start the job";
	}
}

void runInAnotherThread(string cmd) {
	Duration du = dur!"hnsecs"(-2); // Minus value for no waiting
	auto psin = pipe();
	auto psout = pipe();
	auto pserr = pipe();
	spawnShell(cmd, psin.readEnd, psout.writeEnd, pserr.writeEnd , 
null, Config.detached);
	string line;
     while ((line = pserr.readEnd.readln()) !is null){
		receiveTimeout(du, (int dummy) {psin.writeEnd.writeln("q"); 
psin.writeEnd.flush(); }); // Here, entering "q" is app specific 
command to stop.
		writefln("pipe err: %s", line);
		stdout.flush;
	}
}
```
By this way, you can asynchronously process the output from the 
child process.
Jun 28 2023
prev sibling parent Ferhat =?UTF-8?B?S3VydHVsbXXFnw==?= <aferust gmail.com> writes:
On Friday, 23 June 2023 at 23:37:29 UTC, Vinod K Chandran wrote:

 Hi all,
 I am trying to create a program which burns time codes to a 
 video. I am using ffmpeg for this. So far, I can successfully 
 start ffmpeg in another thread and stop it when I need. But I 
 can't read the live outputs from ffmpeg. This is my code.
 ```d
 void onBtnBurnClick(Control c, EventArgs e) {
 	if (!burnStarted) {
 		burnStarted = true;
 		btnBurn.text = "Stop Burning";
 		auto ffCmd = makeFFMPEGCommand(selVideo);
           // ffPipe is a global ProcessPipes
 		auto tsk = task!runFFMPEG(ffCmd, &ffPipe, frm.handle);
 		tsk.executeInNewThread();
 	} else {
 		ffPipe.stdin.writeln("q");
 		ffPipe.stdin.close();
 		btnBurn.text = "Burn Time Code";
 	}
 }
 ```
 This is a button's click event.


I used something similar here:

https://github.com/aferust/oclcv/blob/main/examples/threshold-video/source/app.d
Jun 29 2023