Check where include/library path variables like OpenCV_LIBS point to in unix

Question

When using some libraries like OpenCV with C/C++, variables like OpenCV_LIBS are used to point the compiler/linker to the relevant directories.

Examples using cmake:

include_directories( ${OpenCV_INCLUDE_DIRS} )
target_link_libraries( project_name ${OpenCV_LIBS} )

How can I check where such variables point at? I've tried typing set or printenv in terminal but it shows only some system variables. Also how can I set/change such variables?

Bast

Answer 1

Those variables are determined by cmake (see OpenCVConfig.cmake for a more detailed description of opencv CMake variables available).

To see those values you can add message() calls after the find_package(OpenCV) call to your project's CMakeLists.txt:

find_package(OpenCV)

message(STATUS "OpenCV_INCLUDE_DIRS = ${OpenCV_INCLUDE_DIRS}")
message(STATUS "OpenCV_LIBS = ${OpenCV_LIBS}")

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Alternatively you can run find_package via a CMake command line option.

Here are a few examples (the CMAKE_PREFIX_PATH part is optional if CMake is not able to find your libraries installation path automatically):

1. MODE=COMPILE giving include directories (e.g. with MSVC compiler)

   $ cmake 
       --find-package 
       -DNAME=OpenCV 
       -DCOMPILER_ID=MSVC -DMSVC_VERSION=1700 
       -DLANGUAGE=CXX 
       -DMODE=COMPILE 
       -DCMAKE_PREFIX_PATH:PATH=/path/to/your/OpenCV/build
   

2. MODE=LINK giving link libraries (e.g. with GNU compiler)

   $ cmake 
       --find-package 
       -DNAME=OpenCV 
       -DCOMPILER_ID=GNU 
       -DLANGUAGE=CXX 
       -DMODE=LINK 
       -DCMAKE_PREFIX_PATH:PATH=/path/to/your/OpenCV/build
   

Note: This CMake call will create a CMakeFiles sub-directory in your current working directory.

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References

• Using OpenCV with gcc and CMake
• CMakeFindPackageMode CMake module documentation

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