#583: system function with feedback

I think I'd be worried about spawning too many long-running background processes and hitting the process fd limit (default is 1024 on Linux, I think?).

Counter-proposal: fork(), configure pipes (dup2, I think?), exec(), and then wait for SIGCHLD. Alternatively, since the timer would allow for a poll every so often, could possibly mask SIGCHLD away and just do a waitpid with WNOHANG in the fired timing event to loop over all the bg processes and report on the ones that are done. I can't remember enough about fork and SIGCHLD to know exactly how kosher the second option is, though, so YMMV.