Set Environment Variables for startDetached() QProcess

Question

In Qt4, there is QProcess::setProcessEnvironment() for setting Env variables for the newly spawn process.

However, QProcess::startDetached() is a static member function, so setProcessEnvironment() doesn't apply. How does one set Env variables for a detached process in Qt?

Answer 1

It is a known old bug: http://bugreports.qt-project.org/browse/QTBUG-2284. You need to overload startDetached function to support your own environment. Take a look at Qt sources to see how to do that: http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/io?h=5.5 (qprocess* files).

Answer 2

Using Qt5.5 now, Run into this problem.

Under Win7, Used code below, Set environment in father process, It seems that sub process inherit the environment. Not for sure, but it worked in my case.

Hope there is better solutions

QString oldPath = qgetenv( "Path" );
QByteArray newPath = ( QCoreApplication::applicationDirPath() + ";" + oldPath ).toLocal8Bit();
bool bSet = qputenv("Path", newPath);
if ( !bSet )
{
    qDebug()<<"Failed";
}

Answer 3

This behaviour has been fixed in Qt 5.10.0. However, the order of calls seems to be important. The following example works:

QProcess proc;
QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
env.insert("var-name", "var-value");
proc.setProgram("program-path");
proc.setProcessEnvironment(env);
proc.startDetached();

while this does not work:

QProcess proc;
QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
env.insert("var-name", "var-value");
proc.setProcessEnvironment(env);
proc.startDetached("program-path");