Feature requests: list of PIDS, and all threads

[George Spelvin]

> Of course we can, and you've implemented this with commit
> v4.6-258-ge8172b7 already, but the same effect can be trivially
> achieved by using sed, e.g.
> strace `pgrep whatever |sed 's/^/-p /'`
> so there is no real benefit for users from adding this feature.

I agree it's just syntactic sugar, but it makes certain one-liners
considerably less annoying to type.  (For example, I keep forgetting if
sed requires -e or not.)

I did express it as a wish because "it would make it much easier to...",
not a fundamentally new capability.