mkstemp fails but data still transferred

Steve Traugott stevegt at TerraLuna.Org
Wed Mar 23 08:06:22 GMT 2005

On Tue, Mar 22, 2005 at 11:27:57PM -0600, John Van Essen wrote:
> The Documentation section of the rsync web site has a "How Rsync Works" page:
> originally written by the late JW Schultz.
> In the pipeline section you'll see that communication is unidirectional.
> One of rsync's many advantages is streaming unidirectional pipelines.
> Not having two-way chatter helps speed up file transfers.

...and --write-batch actually depends on this -- the batch file includes
a byte-for-byte copy of the stream of checksums and changed blocks that
are being sent over the wire (or local pipe) to the receiving process
(see "The Sender" section in JW's doc).  

And the --offline patch takes this even further by muting the wire
transmission outright during that part of the protocol; we only record
what *would* have been sent.  (The receiver is perfectly happy to sit
there in silence while we do this.)

Reading the batch in later at the destination with --read-batch is just
a process of feeding to the receiver what it would have heard on the
wire -- the receiver is none the wiser, and goes through the same
motions it would perform in a live session; altering, creating, and
deleting files accordingly.

Think of an rsync batch file (or the unidirectional stream it came from)
as a very compact, binary representation of what might normally be in a
'patch' input file, with the added semantics of mkdir, chmod, chown,
unlink, etc.  It's turning out there are some powerful things that can
be done with this.

Stephen G. Traugott  (KG6HDQ)
UNIX/Linux Infrastructure Architect, TerraLuna LLC
stevegt at TerraLuna.Org -- http://Infrastructures.Org
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