kill nodes (started with .launch file) properly in Qt, how?

asked 2019-05-27 07:11:04 -0600

akosodry
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Hello ROS Community,

i'm currently developing a Qt C++ GUI for a custom made robotic arm.

I have a QPushButton that starts a .launch file (that launches multiple nodes, i.e., the gazebo, robot spawner, controller spawner, move_group, etc.). The terminal output is printed in a QPlainTextEdit. This mechanism works well and is coded as follows.

    m_process=new QProcess;
    connect(m_process, SIGNAL(readyRead()),this,SLOT(onBytesAvailable()));
    connect(m_process, SIGNAL(finished(int,QProcess::ExitStatus)),this,SLOT(onProcessFinished(int,QProcess::ExitStatus)));
    m_process->setProcessChannelMode(QProcess::MergedChannels);
    m_process->start(roslaunch robot5s_gazebo robot5s_bringup_moveit2.launch);
    bool started=m_process->waitForStarted();
    Q_ASSERT(started);

My problem is that i don't know how to kill successfully the aforementioned process, ie., to perform basically CTRL+C.

If i call m_process->kill() i got in my onProcessFinished SLOT that the kill was successful: Process finished, exit code:9 status: 1, however the nodes are still running, the rosnode list gives

/gazebo
/gazebo_gui
/joint_controller_spawner
/move_group
/robot5s_controller_spawner
/robot_state_publisher
/rosout

So i want to ask, how to perform the CTRL+C mechanism for the launched nodes in Qt C++ environment?

Remark: (Even tho i don't want to kill all the nodes, just the ones that were launched) I also tried to create another QProcess that performes rosnode kill -a, but that also did not do the killing successfully, since gazebo kept running.

Thank you in advance.

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Thanks for the quick answer. This does the job:

QProcess* kill_process = new QProcess;

    QString str = "kill -SIGINT " + QString::number(m_process->processId());
    qDebug() << str;
    kill_process->start(str);

    bool started=kill_process->waitForStarted();
    qDebug()<<"Process started:"<<started<<kill_process->errorString();
    Q_ASSERT(started);

akosodry ( 2019-05-27 07:58:06 -0600 )edit

Are you recording the stdout of the roslaunch process? It could be useful to see how it's reacting to the SIGINT and if it is continuing to execute for long enough to kill all the spawned nodes. The only thing I can think is that for some reason the roslaunch process is being killed before it has time shut down all the nodes it's started.

PeteBlackerThe3rd ( 2019-05-27 08:02:31 -0600 )edit

@PeteBlackerThe3rd IT works, just it takes time. In my case it took 15-20 sec to kill all the nodes!

Thanks you very much again!

akosodry ( 2019-05-27 08:06:26 -0600 )edit

Great, glad you got it working.

PeteBlackerThe3rd ( 2019-05-27 08:14:34 -0600 )edit

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kill nodes (started with .launch file) properly in Qt, how?

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kill nodes (started with .launch file) properly in Qt, how?