Question

How can I obtain this information:

• Total Memory
• Free Memory
• Memory used by current running application ?

I think Qt should have memory options, that would be platform-independent, but
I can’t find it. So what can I do when I want to make a platform-independent application that shows memory state?

Answer 1

Unfortunately, there is nothing built into Qt for this. You must do this per-platform.

Here are some samples to get you started. I had to implement this in one of my apps just last week. The code below is still very much in development; there may be errors or leaks, but it might at least point you in the correct direction. I was only interested in total physical RAM, but the other values are available in the same way. (Except perhaps memory in use by the current application … not sure about that one.)

Windows (GlobalMemoryStatusEx)

MEMORYSTATUSEX memory_status;
ZeroMemory(&memory_status, sizeof(MEMORYSTATUSEX));
memory_status.dwLength = sizeof(MEMORYSTATUSEX);
if (GlobalMemoryStatusEx(&memory_status)) {
  system_info.append(
        QString("RAM: %1 MB")
        .arg(memory_status.ullTotalPhys / (1024 * 1024)));
} else {
  system_info.append("Unknown RAM");
}

Linux (/proc/meminfo)

QProcess p;
p.start("awk", QStringList() << "/MemTotal/ { print $2 }" << "/proc/meminfo");
p.waitForFinished();
QString memory = p.readAllStandardOutput();
system_info.append(QString("; RAM: %1 MB").arg(memory.toLong() / 1024));
p.close();

Mac (sysctl)

QProcess p;
p.start("sysctl", QStringList() << "kern.version" << "hw.physmem");
p.waitForFinished();
QString system_info = p.readAllStandardOutput();
p.close();