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Re: No os.copy()? Why not?

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On Wed, 04 Apr 2012 08:14:18 -0400, Roy Smith wrote:

>> And sparse files are really hard to reproduce, at least on Unix: on
>> Linux even the system's cp doesn't guarantee sparseness of the copy (the
>> manual mentions a "crude heuristic").
> 
> I imagine the heuristic is to look for blocks of all zeros.

Yes. Although it's not really accurate to describe it as a "heuristic".

With --sparse=always, it will try to make the output sparse regardless of
whether the input was sparse, replacing any all-zeros block with a hole.

The default of --sparse=auto will only create a sparse file if the input
itself is sparse, i.e. if the length of the file rounded up to the nearest
block exceeds its disk usage.

Regardless of the --sparse= setting and whether the input was sparse, if
it tries to create a sparse file it will create holes wherever possible
rather than attempting to preserve the exact pattern of holes in a sparse
input file.

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Thread

No os.copy()?  Why not? John Ladasky <john_ladasky@sbcglobal.net> - 2012-03-28 13:12 -0700
  Re: No os.copy()? Why not? alex23 <wuwei23@gmail.com> - 2012-03-28 21:50 -0700
    Re: No os.copy()? Why not? John Ladasky <john_ladasky@sbcglobal.net> - 2012-03-30 02:25 -0700
  Re: No os.copy()? Why not? Ian Kelly <ian.g.kelly@gmail.com> - 2012-04-02 14:48 -0600
  Re: No os.copy()?  Why not? HoneyMonster <someone@someplace.invalid> - 2012-04-02 21:11 +0000
    Re: No os.copy()?  Why not? Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-04-03 08:24 +0200
      Re: No os.copy()? Why not? John Ladasky <john_ladasky@sbcglobal.net> - 2012-04-03 02:34 -0700
        Re: No os.copy()? Why not? Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-04-04 14:30 +0200
      Re: No os.copy()? Why not? Ian Kelly <ian.g.kelly@gmail.com> - 2012-04-03 10:29 -0600
  Re: No os.copy()?  Why not? D'Arcy Cain <darcy@druid.net> - 2012-04-03 15:46 -0400
    Re: No os.copy()?  Why not? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-04-04 05:53 +0000
      Re: No os.copy()? Why not? Chris Angelico <rosuav@gmail.com> - 2012-04-04 18:37 +1000
        Re: No os.copy()? Why not? Steve Howell <showell30@yahoo.com> - 2012-04-04 08:15 -0700
      Re: No os.copy()?  Why not? Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2012-04-04 11:22 +0200
        Re: No os.copy()?  Why not? Roy Smith <roy@panix.com> - 2012-04-04 08:14 -0400
          Re: No os.copy()?  Why not? Nobody <nobody@nowhere.com> - 2012-04-04 20:37 +0100
      Re: No os.copy()?  Why not? Roy Smith <roy@panix.com> - 2012-04-04 08:08 -0400
        Re: No os.copy()? Why not? Chris Angelico <rosuav@gmail.com> - 2012-04-04 22:17 +1000
  Re: No os.copy()?  Why not? Tycho Andersen <tycho@tycho.ws> - 2012-04-03 15:10 -0500
  Re: Re: No os.copy()?  Why not? Evan Driscoll <driscoll@cs.wisc.edu> - 2012-04-03 15:21 -0500

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