Why catkin_make behaves differently when run consecutively on same terminal ?

edit

Hi,

I am using Noetic on Ubuntu 20.04. I downloaded a ROS package from official github source. And after making few changes, I executed command catkin_make twice on the downloaded package. As you can see in the below console (terminal) outputs a1 and b2, the two executions of the same command generate different console outputs. (without making any change in code after the 1st execution of catkin_make command)

Also, I noted that after the 2nd execution 'b1' (and not the 1st - a1), my changes were reflecting when I launched a node. Could anyone help me understand the reason behind so ?

Thanks in advance.

CONSOLE OUTPUT a1:

aakash@aakash:~/Desktop/try1/catkin_ws$ catkin_make
Base path: /home/aakash/Desktop/try1/catkin_ws
Source space: /home/aakash/Desktop/try1/catkin_ws/src
Build space: /home/aakash/Desktop/try1/catkin_ws/build
Devel space: /home/aakash/Desktop/try1/catkin_ws/devel
Install space: /home/aakash/Desktop/try1/catkin_ws/install
Creating symlink "/home/aakash/Desktop/try1/catkin_ws/src/CMakeLists.txt" pointing to "/opt/ros/noetic/share/catkin/cmake/toplevel.cmake"
####
#### Running command: "cmake /home/aakash/Desktop/try1/catkin_ws/src -DCATKIN_DEVEL_PREFIX=/home/aakash/Desktop/try1/catkin_ws/devel -DCMAKE_INSTALL_PREFIX=/home/aakash/Desktop/try1/catkin_ws/install -G Unix Makefiles" in "/home/aakash/Desktop/try1/catkin_ws/build"
####
-- The C compiler identification is GNU 9.3.0
-- The CXX compiler identification is GNU 9.3.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Using CATKIN_DEVEL_PREFIX: /home/aakash/Desktop/try1/catkin_ws/devel
-- Using CMAKE_PREFIX_PATH: /home/aakash/Desktop/code1/catkin_ws/devel;/opt/ros/noetic
-- This workspace overlays: /home/aakash/Desktop/code1/catkin_ws/devel;/opt/ros/noetic
-- Found PythonInterp: /usr/bin/python3 (found suitable version "3.8.2", minimum required is "3") 
-- Using PYTHON_EXECUTABLE: /usr/bin/python3
-- Using Debian Python package layout
-- Found PY_em: /usr/lib/python3/dist-packages/em.py  
-- Using empy: /usr/lib/python3/dist-packages/em.py
-- Using CATKIN_ENABLE_TESTING: ON
-- Call enable_testing()
-- Using CATKIN_TEST_RESULTS_DIR: /home/aakash/Desktop/try1/catkin_ws/build/test_results
-- Forcing gtest/gmock from source, though one was otherwise available.
-- Found gtest sources under '/usr/src/googletest': gtests will be built
-- Found gmock sources under '/usr/src/googletest': gmock will be built
-- Found PythonInterp: /usr/bin/python3 (found version "3.8.2") 
-- Found Threads: TRUE  
-- Using Python nosetests: /usr/bin/nosetests3
-- catkin 0.8.8
-- BUILD_SHARED_LIBS is on
-- BUILD_SHARED_LIBS is on
-- Configuring done
-- Generating done
-- Build files have been written to: /home/aakash/Desktop/try1/catkin_ws/build
####
#### Running command: "make -j12 -l12" in "/home/aakash/Desktop/try1/catkin_ws/build"
####
aakash@aakash:~/Desktop/try1/catkin_ws$

CONSOLE OUTPUT b1:

aakash@aakash:~/Desktop/try1/catkin_ws$ catkin_make
Base path: /home/aakash/Desktop/try1/catkin_ws
Source space: /home/aakash/Desktop/try1/catkin_ws ...