QProcess return value

[ivanicy]

Hello!!

I want to create a program that returns a double[]. And I want to execute this program with a QProcess and get this double[]. Is there any way to do this?

Thank you very much!

[JonB]

@ivanicy
No.

A program can only exit with an int status.

If you need to "pass" anything else back, you could:

1. Save it to file, caller reads file.

2. Write to stdout, have caller read that. (That's the same principle as the previous one, just using a stream/pipe instead of a file.)

3. Use sockets or shared memory or other IPC.

4. Give up on it being a separate process, and write it as a separate thread instead, sharing a memory area.

Given your use of QProcess, I think #2 would be the simplest.

[posktomten]

This post is deleted!

[posktomten]

#include <iostream>
#include <stdlib.h>
using namespace std;
int main(int argc, char **argv)
{
	
   double d1 = atof(argv[1]);
   double d2 = atof(argv[2]);
   cout << (d1+d2);

	return 0;
}

Qt program

const QString executablepath = QDir::toNativeSeparators(QCoreApplication::applicationDirPath());
    const QString executable = QDir::toNativeSeparators(executablepath + "/a.out");
    QStringList arg;
    arg << "4.1" << "3.2";
    QProcess *process = new QProcess(nullptr);
    connect(process, &QProcess::readyReadStandardOutput, [process]() {
        QString output = process->readAllStandardOutput();
        double d = output.toDouble();
        qDebug() << "The sum becomes " << d;
    });
    connect(process, &QProcess::readyReadStandardError, [process]() {
        QString err = process->readAllStandardError();
        qDebug() << "error: " << err;
    });
    process->setWorkingDirectory(executablepath);
    process->start(executable, arg);

[aha_1980]

@posktomten said in QProcess return value:

const QString executablepath = QDir::toNativeSeparators(QCoreApplication::applicationDirPath());
const QString executable = QDir::toNativeSeparators(executablepath + "/a.out");

Note: toNativeSeparators is not needed if you pass that result to Qt functions. It is only needed if you want to display that to the user.

Regards

[posktomten]

Yes! You are absolutely right.

//    const QString executablepath = QDir::toNativeSeparators(QCoreApplication::applicationDirPath());
//    const QString executable = QDir::toNativeSeparators(executablepath + "/a.out");
    const QString executablepath = QCoreApplication::applicationDirPath();
    const QString executable = executablepath + "/a.out";
or
    const QString executablepath = QCoreApplication::applicationDirPath();
    const QString executable = executablepath + "/a.out.exe";