Executing custom tasks at configuration time

To execute custom tasks at configuration time, you can use the execute_process function. Common needs for this are if the build requires additional information before a build, or if files need to be updated for any rerun of CMake. Another common case is when either the CMakeLists.txt file or other input files are generated during the configuration step, although this can also be achieved with the specialized configure_file command, as shown later in this chapter.

The execute_process function works very similarly to the add_custom_target and add_custom_command functions we saw earlier. However, one distinction is that execute_process can capture output to stdout and stderr in a variable or files. The signature of execute_process is as follows:

execute_process(COMMAND <cmd1> [<arguments>]
                [COMMAND <cmd2> [<arguments...