Edit: pcd_viewer has not been part of perception_pcl since at least Hydro.
The tool is now called pcl_viewer and is part of the (stand-alone) PCL package: pcl-tools (at least on Debian/Ubuntu). It's not part of ROS.
See #q80836. The OP there answers his own question and states something similar.
Where in the ros.org would i have needed to go to find this bit of info?
I'm not sure this is a "ROS thing".
Please note that PCL is a stand-alone library. It's not a piece of ROS. There are packages that let you use it with ROS, but it's completely stand-alone, and it's development also happens outside of the ROS community.
The Q&A you linked is 8 years old. PCL has moved on, answers get stale. The wiki page you linked also makes no mention of the tool. Nor do any of the other pages about PCL-related packages (such as pcl_ros).
perception_pcl is actually a metapackage that facilitates installation of all ROS PCL wrapping packages. See the wiki page. It being a metapackage also explains why there isn't much content: it doesn't contain any nodes, messages or other ROS-related infrastructure.
Edit 2: I've updated the pcl_perception wiki page (diff) to point readers to pcl_ros and make it clear that package is just a metapackage. Not something that contains any code, libraries or nodes.
Original answer:
you're not giving us much information.
I have already tried sudo apt-get install ros-melodic-perception-pcl but it still does not show up
Did the package install? Did you get any errors? Something else? What is "it" here?
What is the output of dpkg -l | grep perception-pcl?
After source /opt/ros/melodic/setup.bash, what is the output of rospack find perception_pcl?
I am trying to visualize pcd files and have been following this thread here to do it however I am not able to find the perception_pcl command [..]
Please note: pcd_viewer would be the tool. pcl_perception is the package (which hosts the tool).
You cannot execute pcl_perception. Only pcd_viewer.
Originally posted by gvdhoorn with karma: 86574 on 2020-01-27
This answer was ACCEPTED on the original site
Post score: 0
Original comments
Comment by AdamS on 2020-01-27:
Sorry im not sure how much or how little information is required here. I assume by your reply that the package i installed is the right one. The package did install and there was no problems that i was able to see.
Here is the output of your request
dpkg -l | grep perception-pcl
ii ros-melodic-perception-pcl 1.7.0-2bionic.20191211.062537 amd64 PCL (Point Cloud Library) ROS interface stack.
metrolla@metrolla-ThinkPad-11e:~/catkin_ws$ source /opt/ros/melodic/setup.bash
metrolla@metrolla-ThinkPad-11e:~/catkin_ws$ rospack find perception_pcl
[rospack] Error: package 'perception_pcl' not found
metrolla@metrolla-ThinkPad-11e:~/catkin_ws$
The thread i was looking at showed the following command. is this no longer correct?
rosrun perception_pcl pcd_viewer <filename>
Comment by AdamS on 2020-01-27:
@Delb pointed out that pcl-tools was required for me to use pcl_viewer. this was the missing component. How would I have known what needed to be installed given this case? Where in the ros.org would i have needed to go to find this bit of info?
Comment by AdamS on 2020-01-27:
thanks for the insight. I am rather new to working with LiDAR but jumping headfirst into the deepend of ROS is a lot to digest. I actually thought it was part of ROS. Thank you for clarifying this.
