From: Tim Harig on
On 2010-06-23, Tim Harig <usernet(a)ilthio.net> wrote:
> On 2010-06-23, Jens Thoms Toerring <jt(a)toerring.de> wrote:
>> Owner <Owner(a)owner-pc.com> wrote:
>>> On Tue, 22 Jun 2010 23:08:15 +0000, Tim Harig wrote:
>>
>>> I still not quite sure what they're using for buf from the
>>> source file
>>
>>> I'm looking at putfile routine guessing it read one line
>>> by one line and saves to buf file

The man page might help you:

ftp://ftp.math.utah.edu/pub/mirrors/minnie.tuhs.org/PDP-11/Trees/2.11BSD/usr/man/cat1/ed.0

See append() and gettty() for details on how lines are buffered.