Copy file from source directory to binary directory using CMake - cmake

Question

I'm trying to create a simple project on CLion. It uses CMake 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.

Answer 2

Both option are valid and targeting two different steps of your build:
file(COPY ... copies the file during the configuration step and only in this step. When you rebuild your project without having changed your cmake configuration, this command won't be executed.
add_custom_command is the preferred choice when you want to copy the file around on each build step.
The right version for your task would be:
add_custom_command(
TARGET foo POST_BUILD
COMMAND ${CMAKE_COMMAND} -E copy
${CMAKE_SOURCE_DIR}/test/input.txt
${CMAKE_CURRENT_BINARY_DIR}/input.txt)
you can choose between PRE_BUILD, PRE_LINK, POST_BUILD
best is you read the documentation of add_custom_command
An example on how to use the first version can be found here: Use CMake add_custom_command to generate source for another target

Answer 3

The first of option you tried doesn't work for two reasons.
First, you forgot to close the parenthesis.
Second, the DESTINATION should be a directory, not a file name. Assuming that you closed the parenthesis, the file would end up in a folder called input.txt.
To make it work, just change it to
file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/input.txt
DESTINATION ${CMAKE_CURRENT_BINARY_DIR})

Answer 4

I would suggest TARGET_FILE_DIR if you want the file to be copied to the same folder as your .exe file.
$
Directory of main file (.exe, .so.1.2, .a).
add_custom_command(
TARGET ${PROJECT_NAME} POST_BUILD
COMMAND ${CMAKE_COMMAND} -E copy
${CMAKE_CURRENT_SOURCE_DIR}/input.txt
$<TARGET_FILE_DIR:${PROJECT_NAME}>)
In VS, this cmake script will copy input.txt to the same file as your final exe, no matter it's debug or release.

Answer 5

The suggested configure_file is probably the easiest solution. However, it will not rerun the copy command to if you manually deleted the file from the build directory. To also handle this case, the following works for me:
add_custom_target(copy-test-makefile ALL DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/input.txt)
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
DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/input.txt)

Answer 6

if you want to copy folder from currant directory to binary (build folder) folder
file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/yourFolder/ DESTINATION ${CMAKE_CURRENT_BINARY_DIR}/yourFolder/)
then the syntexe is :
file(COPY pathSource DESTINATION pathDistination)

Answer 7

This is what I used to copy some resource files:
the copy-files is an empty target to ignore errors
add_custom_target(copy-files ALL
COMMAND ${CMAKE_COMMAND} -E copy_directory
${CMAKE_BINARY_DIR}/SOURCEDIRECTORY
${CMAKE_BINARY_DIR}/DESTINATIONDIRECTORY
)

Answer 8

If you want to put the content of example into install folder after build:
code/
src/
example/
CMakeLists.txt
try add the following to your CMakeLists.txt:
install(DIRECTORY example/ DESTINATION example)