Copy file from source directory to binary directory using CMake

Question

I'm trying to create a simple project on CLion. It uses CMake (I'm new here) to generate Makefiles to build project (or some sort of it)

All I need to is transfer some non-project file (some sort of resource file) to binary directory each time when I run the my code.

That file contains test data and application open it to read them. I tried several ways to do so:

• Via file(COPY ...

  file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/input.txt
          DESTINATION ${CMAKE_CURRENT_BINARY_DIR}/input.txt
  

  Looking good but it work just once and not recopy file after next run.

• Via add_custom_command

  • OUTPUT version

    add_custom_command(
            OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/input.txt
            COMMAND ${CMAKE_COMMAND} -E copy
                    ${CMAKE_CURRENT_SOURCE_DIR}/input.txt
                    ${CMAKE_CURRENT_BINARY_DIR}/input.txt)
    

  • TARGET version

    add_custom_target(foo)
    add_custom_command(
            TARGET foo
            COMMAND ${CMAKE_COMMAND} copy
                    ${CMAKE_CURRENT_BINARY_DIR}/test/input.txt
                    ${CMAKE_SOURCE_DIR})
    

  But no one of it work.

What am I doing wrong?

Answer 1

You may consider using configure_file with the COPYONLY option:

configure_file(<input> <output> COPYONLY)

Unlike file(COPY ...) it creates a file-level dependency between input and output, that is:

If the input file is modified the build system will re-run CMake to re-configure the file and generate the build system again.