Chapter1_9_18_2022
   ROS Robotics by Example 2nd
Alias foxy or noetic
harman@harman-VirtualBox:~$ noetic    (**********  Make sure that ROS distribution is Sourced!!!)
  ROS_DISTRO was set to 'foxy' before. Please make sure that the environment does not mix paths from    different  distributions.


harman@harman-VirtualBox:~$ sudo apt install rospack-tools   (If not there!)
 [sudo] password for harman: 
 Reading package lists... Done
  ........
 harman@harman-VirtualBox:~$ rospack help | less     Pg11 (q to quit)
  USAGE: rospack <command> [options] [package]
  Allowed commands:
    help
    cflags-only-I     [--deps-only] [package]
    cflags-only-other [--deps-only] [package]
   ''''''''' 
     find [package]
''''''''''
http://wiki.ros.org/ROS/CommandLineTools

harman@harman-VirtualBox:~$ roscd turtlesim            (Go To Package - Pg 11)
harman@harman-VirtualBox:/opt/ros/noetic/share/turtlesim$ 

 harman@harman-VirtualBox:/opt/ros/noetic/share/turtlesim$ cd ~  (Go Home)
harman@harman-VirtualBox:~$ rosls turtlesim             (Note - from Anywhere! Pg 11)
  cmake  images  msg  package.xml  srv
 
harman@harman-VirtualBox:~$ rosls turtlesim/images       (Pg 12)
 box-turtle.png   groovy.png  indigo.svg   lunar.png    palette.png
 diamondback.png  hydro.png   jade.png     lunar.svg    robot-turtle.png
 electric.png     hydro.svg   kinetic.png  melodic.png  sea-turtle.png

harman@harman-VirtualBox:~$ roscd turtlesim/    (Pg12)
harman@harman-VirtualBox:/opt/ros/noetic/share/turtlesim$ cat package.xml
 <package>
  <name>turtlesim</name>
  <version>0.10.2</version>
  <description>
    turtlesim is a tool made for teaching ROS and ROS packages.
( A list of urls to find wiki, bugtracker, github)
( A list of build depends such as roscpp, std_msg, ...)
(A list of run_depend  geometry_msgs, roscpp, rostime, std_msgs, ...)

harman@harman-VirtualBox:/opt/ros/noetic/share/turtlesim$ cd ~   (Home)
harman@harman-VirtualBox:~$ rospack find turtlesim
   /opt/ros/noetic/share/turtlesim

harman@harman-VirtualBox:~$ rospack list       (A long list of packages WITH directories)
............
turtlesim /opt/ros/noetic/share/turtlesim
...........

harman@harman-VirtualBox:~$ rospack list-names  Pg 13
 actionlib
 actionlib_msgs
 actionlib_tutorials
...
 rospy_tutorials, roswtf, 
 turtlesim
 urdf, ...........

harman@harman-VirtualBox:~$ rospack list-names | grep turtleharman@harman-VirtualBox:~$ rospack list

 turtle_actionlib
 turtle_tf
 turtle_tf2
 turtlesim
 
 ------------------  Page 16-17
Alias foxy or noetic                 (Terminal 1)
harman@harman-VirtualBox:~$ noetic
ROS_DISTRO was set to 'foxy' before. Please make sure that the environment does not mix paths from different distributions.
harman@harman-VirtualBox:~$ roscore   (Leave Terminal Open - Minimized)
PARAMETERS
  * /rosdistro: noetic
  * /rosversion: 1.15.14
 auto-starting new master
 process[master]: started with pid [4145]
 ROS_MASTER_URI=http://harman-VirtualBox:11311/

NEW Terminal  (Terminal 2)
lias foxy or noetic
harman@harman-VirtualBox:~$ noetic
harman@harman-VirtualBox:~$ rosnode list
   /rosout                (Reveives Debug messages for example)
http://wiki.ros.org/rosout  (rosout is the name of the console log reporting mechanism in ROS.)

harman@harman-VirtualBox:~$ rostopic list
 /rosout
 /rosout_agg          (Just subscribes to the /rosout node - not all the nodes.)
http://wiki.ros.org/rosout
rosout subscribes to the standard /rosout topic, records these messages in a textual log file, and rebroadcasts the messages on /rosout_agg.

...............  TURTLESIM  PG 19 .........  LET'S MOVE
Due to their heavy shells, turtles are slow-moving on land. A desert tortoise moves at only 0.22–0.48 km/h (0.14–0.30 mph). By contrast, sea turtles can swim at 30 km/h (19 mph)   WOW!

http://wiki.ros.org/turtlesim