I have a setup like this:
In which the yellow command blocks are a standard 20Hz /fill clock, and the blue is a command such as, for example:
/spreadplayers ~ ~ 10 20 false @p[r=5]
My problem, which has cropped up for me quite a few times, is that I want to get some kind of redstone pulse or output when the blue command block succeeds. The obvious solution is a comparator, but that does not work for this as the command executes once and then fails on the next tick, resetting its successcount before the comparator can detect it.
Ideally this output detection should also be pretty fast, although it doesn't have to work at the same frequency as the fill clock. The solution needs to actually be testing for if the command succeeded.
I have tried some things with /blockdata and /testforblock, but no success as of yet.
Edit: Again, the solution needs to actually test for the block succeeding. It cannot just test for, say, the players location, because the command block will not always do something that can be tested for. Imagine that instead it is a /say, relative /fill, or /clear item command.