A package that launches the map_server node?

Course Support ROS Navigation In 5 Days
1

I had an error in the 3th unit in excercie 2.5 : I am supposed to create a launch file that launches the map_server node:
The package that i am going to create won’t contain any source code file , so I didn’t know what the argument type should include!

I thought that the launch file would look like that , but I got an error:
<launch> <node pkg="provide_map" name="my_map_name" output="screen"> </node> </launch>

rrrrrrrrrrrr
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2

Can you show your launch file?
And did you already create your map?

3

I have already created and saved the map . Its name is ‘my_map_name’
And there is my launch file ,I have just edited the post.

4

If you already created the map, you have to add the path of the map to your launchfile as an argument
You can use the $(find mypackage) command too, so like args=“$(find mypackage)/map/my_map.yaml”

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5

Did you created there a py or cpp src code file in that package ? Because the excercie didn’t mention that and I didn’t even include a type attribute as you see above and I still get an error : attrivbute missing. Should I create a src code file? If yes what should be there?

6

Hi @mouidsakka01 ,

It goes by default that if the type in launch file does not indicate a .py extension, then the file type is a .cpp.

So, to be clear, when you launch map_server node, you call map_server package that contains the map_server cpp file whose name is also map_server. The argument you provide is the path to your map file that you have saved when you created your mappping.

Regards,
Girish

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8

I knew that the package map_server contained a cpp file. But why when I navigated there to check it up I couldn’t find it?

mok
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I mean aren’t the nodes map_server and map_saver are supposed to be found there in some source file? Idk maybe this has to do with cmake , which I still don’t know what it is.

9

Hi @mouidsakka01 ,

map_server provides the map_server ROS Node, which offers map data as a ROS Service. It also provides the map_saver command-line utility, which allows dynamically generated maps to be saved to file.
Source: https://wiki.ros.org/map_server

map_server node source: navigation/map_server/src/main.cpp at noetic-devel · ros-planning/navigation · GitHub

That is because you are looking in the wrong directory.

user:~$ cd /opt/ros/noetic/lib/map_server/
user:/opt/ros/noetic/lib/map_server$ ls -la
total 272
drwxr-xr-x 1 root root   4096 Sep 17  2021 .
drwxr-xr-x 1 root root  20480 Jan 12  2022 ..
-rwxr-xr-x 1 root root   3942 Aug 27  2020 crop_map
-rwxr-xr-x 1 root root  88544 Jul 27  2021 map_saver
-rwxr-xr-x 1 root root 158344 Jul 27  2021 map_server   <--- executable!
user:/opt/ros/noetic/lib/map_server$

System framework packages will always be in a secured location. It won’t be in open-access location like the path of roscd map_server so that people won’t mess around with important original files!

Regards,
Girish

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