Find child processes

[rajji_saini]

Hi ,

My project works on both Linux and Windows. So I want to be able to find a common/unique way to get the list of child processes of a process(QProcess). So that when I kill the main process I kill the child/descendants as well.

Regards,
Raj

[high_flyer]

This is system specific.
There is no common way to do it.

[rajji_saini]

Could you please lead me to a link or example for windows and Linux ??

[high_flyer]

sure:
here

[rajji_saini]

This works on windows:

void winTerminateChildProcesses()
{
    HANDLE hProcessSnap;
    PROCESSENTRY32 pe32;
 
 // Take a snapshot of all processes in the system.
    hProcessSnap = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
    if( hProcessSnap == INVALID_HANDLE_VALUE )
    {
        qDebug() << "Error: CreateToolhelp32Snapshot";
        return;
    }
 
     // Set the size of the structure before using it.
     pe32.dwSize = sizeof( PROCESSENTRY32 );
 
     // Retrieve information about the first process,
     // and exit if unsuccessful
     if( !Process32First( hProcessSnap, &pe32 ) )
     {
        qDebug() << "Error: Process32First";
        CloseHandle( hProcessSnap ); // clean the snapshot object
        return;
     }
 
    ProcTree procTree;
 
    // Now walk the snapshot of processes, and
    // display information about each process in turn
    do
    {
        procTree[pe32.th32ParentProcessID] << pe32.th32ProcessID;
    }
    while( Process32Next( hProcessSnap, &pe32 ) );
 
    CloseHandle( hProcessSnap );
 
    QHashIterator<DWORD, QSet<DWORD>> i(procTree);
    while (i.hasNext()) {
        i.next();
        qDebug() << i.key() << ": " << i.value() << endl;
    }
 
}

void winTerminateChildProcesses()
{
    HANDLE hProcessSnap;
    PROCESSENTRY32 pe32;

 // Take a snapshot of all processes in the system.
    hProcessSnap = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
    if( hProcessSnap == INVALID_HANDLE_VALUE )
    {
        qDebug() << "Error: CreateToolhelp32Snapshot";
        return;
    }

     // Set the size of the structure before using it.
     pe32.dwSize = sizeof( PROCESSENTRY32 );

     // Retrieve information about the first process,
     // and exit if unsuccessful
     if( !Process32First( hProcessSnap, &pe32 ) )
     {
        qDebug() << "Error: Process32First";
        CloseHandle( hProcessSnap ); // clean the snapshot object
        return;
     }

    ProcTree procTree;

    // Now walk the snapshot of processes, and
    // display information about each process in turn
    do
    {
        procTree[pe32.th32ParentProcessID] << pe32.th32ProcessID;
    }
    while( Process32Next( hProcessSnap, &pe32 ) );

    CloseHandle( hProcessSnap );

    QHashIterator<DWORD, QSet<DWORD>> i(procTree);
    while (i.hasNext()) {
        i.next();
        qDebug() << i.key() << ": " << i.value() << endl;
    }

}

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[rajji_saini]

Just to avoid confusion :- ProcTree here is a QHash

typedef QHash<DWORD, QSet<DWORD> > ProcTree;

[wysota]

On Linux there is a concept of process groups. When you kill a group leader, all its children die automatically.