A question about rsync

Guo jing
2004-05-31T14:35:37Z

hello,
  I am a student in China.I like the linux and usually use the rsync to
backup my documents. Last week when I use it,I find a question I want to
discuss with you.

   The condition is like this: The source file that I want to rsync to
another computer is 129M before I start the rsync. During the running of
the rsync,the file was changed and became to about 50M, then the rsync
ended. When I view the destination, I found that the file was 129M. And
there were some contents of the files added when the rsync was running.

  After that, I do some tests about the rsync:

       1. After I start the rsync to backup a file, I delete the file
during the rsync is running, I found the file can been backuped normally.
       2. While the rsync is backuping a file name sourfile (50M), I add
some content by the command "cat addfile >> sourfile" to enlarge
the file
to 100M. After the rsync finished.I found the file is still 50M.

    The question is that , how the rsync copy a file to another computer at
the first time ? My attitude is that it remenbers the physical blocks the
file used when the rsync scaned. Then ,rsync will send the blocks to the
destination no matter if the file or the block has changed. So, is that
right?? Who can tell me how the rsync decide which contents should to send
to the destiation?

  Sorry, my English is very poor. Thanks for your read and answer!!

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