pid vs processId

[Dijkstra]

what is the difference between pid and processId and which should i use to kill the process and how to kill it

[SGaist]

Hi,

What are you talking ? QProcess ? If so, how do you use it ?
If not, what are you doing ?
What code are you using ?

[Dijkstra]

@SGaist yes qprocess i start the servers in this function

void ApplicationEngine::checkAndStartServers()
{

    std::cout << "checking thrift" << std::endl;
    QProcess systemCheck;
    systemCheck.start("/bin/bash",QStringList() << "-c" << "ps -aux | grep \'[V]iBEDBi.py\' | wc -l");
    systemCheck.waitForFinished();
    QString output(systemCheck.readAllStandardOutput());
    int numInstants = output.toInt();
    if(numInstants < 1)
    {
      std::cout << "thrift has not started" << std::endl;
      std::cout << "starting thrift" << std::endl;
      thriftProcess.start("/bin/bash",QStringList() << "-c" << "cd /home/avidbeam/DB-management/ThriftDBi && python ViBEDBi.py");
      cout<<thriftProcess.pid();
    }
    else
    {
        std::cout << "Thrift already running\n";
        std::cout << "number of runnign thrift instants is: \n" << output.toStdString() << std::endl;
    }

    std::cout << "checking detection server" << std::endl;
    systemCheck.start("/bin/bash",QStringList() << "-c" << "ps -aux | grep \'[d]etection-server.json\' | wc -l");
    systemCheck.waitForFinished();
    output =QString(systemCheck.readAllStandardOutput());
    numInstants = output.toInt();
    if(numInstants < 1)
    {
      std::cout << "detection-server has not started: starting now ..." << std::endl;
      detectionServerProcess.start("/bin/bash",QStringList() << "-c" << "cd /home/avidbeam/workspace/ATUN_plugins/Phoenix_1_1_0/avidauto-plugin/submodules/detector && /usr/local/lib/ViBESDK_exe -j detection-server.json -v 3");
    }
    else
    {
        std::cout << "detection-server already started: \n" << output.toStdString() << std::endl;
    }

    std::cout << "checking recognition server" << std::endl;
    systemCheck.start("/bin/bash",QStringList() << "-c" << "ps -aux | grep \'[r]ecognition-server.json\' | wc -l");
    systemCheck.waitForFinished();
    output =QString(systemCheck.readAllStandardOutput());
    numInstants = output.toInt();
    if(numInstants < 1)
    {
      std::cout << "recognition-server has not started: starting now ..." << std::endl;
      recognitionServerProcess.start("/bin/bash",QStringList() << "-c" << "cd ~/workspace/ATUN_plugins/Phoenix_1_1_0/avidauto-plugin/submodules/ocr && /usr/local/lib/ViBESDK_exe -j recognition-server.json -v 3");
    }
    else
    {
        std::cout << "recognition-server already started: \n" << output.toStdString() << std::endl;
    }

}

and after i finish i want to create a function to check if those servers stoped by checking if their pid is 0 or not and if not i want to kill them

[JonB]

@Dijkstra
A couple of observations:

• You start your second ps too soon after you have spawned your detectionServerProcess. Since you don't wait, there is certainly a chance your _exe will not have started yet.

• I would not be running bash/ps/grep/wc processes. I would be looking in the Linux /proc vfs.

• If you really want kill you'll want to run kill, or you might go for pkill and save on half this stuff. Or you might call kill() function directly (man kill(2)).

• You might look at have your shell script get the pid of the process created and return it, instead of all this ps looking up.

• You might be better moving more/all of the logic into the shell script (e.g. supply a shell script file with your app) instead of doing half of it here in your C++ code, and hard-coded at that. It also may make it easier to adapt if there are problems/changes/enhancements required, rather than have to alter your C++ code.

There is also QProcess::terminate/kill(), though they might not work well with the way you are spawning. If your _exe is a "server" (Linux demon) you probably ought be using QProcess::startDetached() rather than start().

[Dijkstra]

@JonB so checking the pid then using .kill() is not going to work or what

if(thriftProcess.pid()){
        thriftProcess.kill();
    }
    if(detectionServerProcess.pid()){
        detectionServerProcess.kill();
    }
    if(recognitionServerProcess.pid())
        recognitionServerProcess.kill();

[JonB]

@Dijkstra
Depends on how your various executables behave, and bash. Try this i.e. (kill(1), and you may or may not have to go kill -9 ...) from a terminal/shell outside of Qt.

[Dijkstra]

@JonB
what about this

QProcess systemcheck,kill;
    systemcheck.start("/bin/bash",QStringList() << "-c" << "ps -aux | grep chrome | awk '{print $2}'");
    systemcheck.waitForFinished();
    QString output(systemcheck.readAllStandardOutput());
    QStringList pids=output.split('\n');
    pids.pop_back();
    //cout<<output.toStdString()<<endl;
    if(pids.size()){
        for(auto it:pids){
            kill.start(QString("kill -9 %1").arg(it.toInt()));
            cout<<it.toInt()<<endl;
        }
    }

i get the pid's of the process i am searching for and adding them to a list and running the kill command on them i really dont know what i am supposed to do after i run this it outputs this

535
QProcess::start: Process is already running
556
QProcess::start: Process is already running
676
QProcess::start: Process is already running
678
QProcess::start: Process is already running
5690
QProcess::start: Process is already running
5700
QProcess::start: Process is already running
5701
QProcess::start: Process is already running
5702
QProcess::start: Process is already running
5705
QProcess::start: Process is already running
5726
QProcess::start: Process is already running
5729
QProcess::start: Process is already running
5742
QProcess::start: Process is already running
5789
QProcess::start: Process is already running
5812
QProcess::start: Process is already running
5838
QProcess::start: Process is already running
6115
QProcess::start: Process is already running
22797
QProcess::start: Process is already running
31396
QProcess::start: Process is already running
31834
QProcess::start: Process is already running
32434
QProcess: Destroyed while process ("kill") is still running.```

[jsulm]

@Dijkstra said in pid vs processId:

kill.start(QString("kill -9 %1").arg(it.toInt()));

This is wrong. Use the static https://doc.qt.io/qt-5/qprocess.html#execute method...
Also, parameters are passed as string list as described in the documentation.

[JonB]

@Dijkstra
I'll say it again, and then leave to you: for the complexity/number of calls/amount of hard-coding you're doing, I would move all this logic into external script files. Up to you.

[Dijkstra]

@jsulm

if(pids.size()){
        for(auto it:pids){
            QProcess::execute("kill -9 ",QStringList()<<it);
            cout<<it.toInt()<<endl;
        }
    }

like this ?

[JonB]

@Dijkstra
No, because kill -9 is not a command! QProcess::execute("kill", QStringList()<< "-9" << it);

[Dijkstra]

@JonB it worked thank you