Eric Schrock wrote:

You have a couple different things in play here.

First, MDB pipelines only work with uintptr_t's, not arbitrary text. So when you try to pipe something like "foo: X" or "X Y Z" to another dcmd, the parser will choke.

Normally, the formatting commands ('/' and friends) recognize when you are in pipe context and omit any extraneous formatting characters. Since they only output numbers, they are safe to use in pipe context.

However, under ::eval, any notion of pipe context is (intentionally) ignored. So ::eval '/Kn' will print the extra formatting characters (such as "swap_vnodes:") as it has no way of knowing it's being used in pipe context outside the eval context. One way to get around this is to do something like:

::array ... p | ::eval '<p/Kn | =Kn' | ::grep .==0