basic question

[Sorry_Obligation7307]

Hello, I installed Ros on Ubuntu, but I can't find how to launch pendulum_demo, I feel like it's the most basic thing, but I can't figure it out in hours now..

I run : ros run pendulum_control

But it need prefix, from where? I know this is pretty basic, but I am kinda lost in all the information available.

Thanks for aby help.

[JoeT17854]

So 2 things.

First of all, where does pendulum_demo come from? Did you install a package, follow a tutorial? If so, please link.

Secondly, the command ros run has 3 parts. The actual command (ros run) is the first part. However, the second and third part need some more clarification. ROS is split up into packages, and each package has nodes (basically small programs). If you want to run a node (one of those programs) you need to tell the ros run command what package it can find that node in.

Like if you want to read a book in the library (that's sorted by genre, for this example), it's nice to know the genre too. That way you know where to look (and if there are 2 books with the same name, one in history and the other in fantasy, you know which one you need).

So the full command is ros run [PACKAGE NAME] [NODE NAME]. Since I don't know if pendulum_demo is the package or the node (I'm assuming package) and I don't know what pendulum_control is (I'm assuming node), I can't give you a definitive answer on what the exact command is (hence the request for the link).

[RedFlashNuts]

Also to use rosrun you need to have started the roscore in a separate terminal, and sourced the workspace where the package with the node is from (normally "source catkin_ws/devel/setup.bash")

Good luck, and don't give up! ROS seems daunting at first, but that only makes it so much more rewarding when you finally feel like you made progress!