WEBVTT 00:00.050 --> 00:05.900 In your roster application, you may want to launch the same node multiple times, but with a different 00:05.900 --> 00:06.920 configuration. 00:06.950 --> 00:12.320 For example, if you have a node that you've written for a temperature sensor and if you have five temperature 00:12.320 --> 00:17.450 sensors, then you will want to launch the same node five times and of course with a different name 00:17.450 --> 00:18.830 for each sensor. 00:18.860 --> 00:24.590 Because what I just told you in the previous lesson is that you cannot have two nodes with the same 00:24.590 --> 00:25.160 name. 00:25.190 --> 00:26.960 Actually, let's try that first. 00:26.960 --> 00:33.080 So I'm going to run my pi node executable from the Python package in this terminal. 00:33.080 --> 00:35.810 And then I'm going to run it again in that terminal. 00:35.810 --> 00:37.040 And let's see what happens. 00:37.040 --> 00:38.360 So I run it here. 00:38.360 --> 00:39.260 It works. 00:39.830 --> 00:41.030 I run it here. 00:41.030 --> 00:42.800 And it also works. 00:42.800 --> 00:44.780 We don't have any error here. 00:44.780 --> 00:49.160 But then let's do a ros2 node list. 00:49.160 --> 00:52.190 And you see we have here a warning. 00:52.190 --> 00:58.670 Be aware that there are nodes in the graph that share an exact name, which can have unintended side 00:58.670 --> 00:59.150 effects. 00:59.180 --> 01:03.140 Okay, so you might have weird errors if you have stuff like this. 01:03.170 --> 01:06.830 Okay, so better to avoid it and how to solve that. 01:06.860 --> 01:12.740 Well, very simply you can rename the node at runtime when you start it with Ros2 run. 01:12.890 --> 01:13.100 Okay. 01:13.130 --> 01:14.150 So that's what we're going to do. 01:14.180 --> 01:19.250 So let's clear that first and how to rename a node. 01:19.250 --> 01:22.160 Well let's go back to that command Ros2. 01:22.190 --> 01:25.910 Run package name and executable name. 01:25.910 --> 01:33.680 Then we can add arguments after this command with dash dash ros dash args. 01:34.010 --> 01:34.520 Okay. 01:34.520 --> 01:37.550 So every time we add arguments we're going to see later. 01:37.550 --> 01:45.500 Also for parameters and other stuff you will first need to add ros args once only once after the ros 01:45.530 --> 01:45.860 args. 01:45.890 --> 01:50.120 Now let's do a renaming or also called a remapping. 01:50.120 --> 01:53.750 So to do that you need to provide a dash R option. 01:53.930 --> 02:02.120 And then to rename a node you need to do underscore underscore node like that colon equal. 02:02.120 --> 02:03.470 And then the new name. 02:03.470 --> 02:06.710 So for example let's name it a, b, c. 02:06.950 --> 02:11.900 Okay, so if I press enter here, you see that the node is started. 02:11.900 --> 02:14.300 But this time you see the name is ABC. 02:14.390 --> 02:21.920 If I do a ros2 node list I have ABC and I can start, for example, the other one with no renaming. 02:21.920 --> 02:26.120 And this time we have py test and ABC. 02:26.120 --> 02:29.120 So we have no name conflicts okay. 02:29.150 --> 02:33.200 And then I can do Ctrl c again here and let's come back to this. 02:33.200 --> 02:39.080 So the dash R is actually the small variation for the dash dash remap okay. 02:39.110 --> 02:42.590 So that's gonna also work okay. 02:42.620 --> 02:47.180 So you can use dash dash remap or just dash R. 02:47.210 --> 02:50.990 And here let's say that it's going to be a temperature sensor node okay. 02:51.020 --> 02:54.050 Let's imagine you have written a temperature sensor node. 02:54.050 --> 03:00.620 And let's say you want to name it temperature sensor one okay. 03:00.620 --> 03:04.400 And you're going to run that one with. 03:04.910 --> 03:16.560 So you're going to do this and then dash dash Ross AGS dash r underscore underscore node and temperature 03:16.860 --> 03:18.150 sensor two. 03:18.180 --> 03:18.570 Okay. 03:18.600 --> 03:21.210 So you can run the two like that. 03:21.210 --> 03:26.070 And you see now we have temperature sensor one and temperature sensor two. 03:26.100 --> 03:30.720 So that's an example of what you can do if you have a sensor like that. 03:30.720 --> 03:37.230 So as you can see renaming a node at runtime is quite useful because first while you don't have to change 03:37.230 --> 03:40.440 anything in the code okay, the value we have written in the code. 03:40.440 --> 03:41.970 So here it's by test. 03:42.090 --> 03:44.970 This value is not completely hardcoded okay. 03:45.000 --> 03:47.130 You can change it at runtime. 03:47.130 --> 03:52.230 So it's quite dynamic and you don't need to reinstall or recompile any code. 03:52.230 --> 03:59.010 And we're going to come back often to this Ross args and all the arguments we can add after here during 03:59.010 --> 03:59.550 this course. 03:59.550 --> 04:02.160 Because we can also rename more things. 04:02.160 --> 04:03.750 We can rename communications. 04:03.750 --> 04:07.320 So topics services etc. we can also add parameters. 04:07.320 --> 04:10.230 So we're going to come back to this all along the course.