Check for process on multiple platforms?

Question

I'm using Qt, QProcess to launch a process, but there is presently no way to use QProcess to check existing running processes.

I need a way of achieving this on multiple platforms. I have an application name that I want to look up, if its running I want to get it's PID. If it isn't running I will create an instance of it, this last bit I can do.

I'm working on a Mac and so far I've done the following:

pid_t pid = fork();

if ( pid > 0 ) {
    int intStatus;
    while ( (pid = waitpid(-1, &intStatus, WNOHANG)) == 0) {
        system("ps -A");
        qDebug() << "Still waiting!";
        sleep(20);
    }
    qDebug() << "Exit Status %d" << WEXITSTATUS(intStatus);
}

The above executes the command and the output is dumped in the console, I need to capture this so I can process it.

Also looking for a way to achieve this on Windows platforms.

Answer 1

On Posix systems, you could capture the output of ps by using popen and then parse it. The popen part looks like this:

#include <iostream>
#include <cstdio>

int main()
{
    FILE *f = popen ("ps -A", "r");
    char s [1024];
    while (fgets (s, sizeof (s), f))
        std::cout << s;
    pclose (f);
}

Live demo