The new example is shorter but illustrates the
interesting parts of the Unix function and methods.

Change-Id: Ief8ec38909d4ed7829e8d3da58e7b7f712537f99
Reviewed-on: https://go-review.googlesource.com/82079
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>