Which solution is better?

I want to make a scheduler with C++ on Linux.
In the C++ program, I have a scheduler and a function (not relevant to the scheduler – it will return a string). When I want to schedule a task, c++ will call the function and return values on the time setting.
Using cron job on Linux. C++ will run the script and get the output.
Using boost asio for the scheduler. It runs a thread, waits until the time, and wakes up and runs the function.