[cstrahan]

> the current problem is that you don't want to have to copy all file descriptors if all you're going to do is call "exec" and reduce them to three: in, out, err.

To be clear, exec does not necessarily close all but the first three fds -- by default all fds will be inherited. However, you can set the close-on-exec flag on each individual fd (in fact, that's what the Go stdlib does behind the scenes).

Search for FD_CLOEXEC in fcntl(2) and open(2) and you'll see what I'm referring to.

http://man7.org/linux/man-pages/man2/fcntl.2.html

http://man7.org/linux/man-pages/man2/open.2.html