Silence custom command depending on CMAKE_VERBOSE_MAKEFILE

Question

I\'ve a custom command in my CMake script which generates a lot of output. I\'d like to take advantage of CMAKE_VERBOSE_MAKEFILE so I can decide if I want to see this output or

Answer 1

As SirDarius pointed out, execute_process() has an option to silence tool output, while add_custom_command() / add_custom_target() do not.

But there is a way to work around this: By putting the actual call to your tool in a separate CMake script wrapper, using execute_process() with OUTPUT_QUIET enabled or disabled depending on a switch:

# mycustom_command.cmake
if ( OUTPUT )
    execute_process( COMMAND mycustom_command )
else()
    execute_process( COMMAND mycustom_command OUTPUT_QUIET )
endif()

Then, use add_custom_command() and the CMake script processing mode (-P) to call that script from your main CMakeLists.txt, with the script switch enabled / disabled by whatever variable you use for that purpose in your CMakeLists.txt file.

add_custom_command( OUTPUT outfile
                    COMMAND ${CMAKE_COMMAND} -P mycustom_command.cmake -DOUTPUT=${OUTPUT_DESIRED}
                  )

This is fully portable. If your mycustom_command is build from within your project as a target, just add it as DEPENDENCY to your add_custom_command() to have it build in time for the script call.