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Date: | Tue, 5 Dec 2023 14:53:01 +0100 |
To: | cygwin AT cygwin DOT com |
Subject: | Re: Cygwin api to punch a hole into a file? |
Message-ID: | <ZW8rPaJ5jua08WHH@calimero.vinschen.de> |
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From: | Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com> |
Reply-To: | cygwin AT cygwin DOT com |
Cc: | Corinna Vinschen <corinna-cygwin AT cygwin DOT com> |
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On Dec 5 07:36, Thomas Wolff via Cygwin wrote: > > > Am 01.12.2023 um 12:02 schrieb Corinna Vinschen via Cygwin: > > On Dec 1 11:22, Cedric Blancher via Cygwin wrote: > > > Not all filesystems have a 128k block/stripe size, and certainly most > > > filesystems have smaller minimum hole sizes than 128k (e.g. 512bytes > > > is common, ref pathconf _PC_MIN_HOLE_SIZE). > > There's no _PC_MIN_HOLE_SIZE in Linux or POSIX. In Windows, a sparse > > file uses chunks of 64K. You can see this even with a file of just > > a single block. Try this: > > > > $ touch x > > $ chattr +S x > > > > $ echo 1234567890123456789012345678901234567890123456789012345678901234567890123456789 >> x > > $ ls -ls x > > 1 -rw-r--r-- 1 corinna vinschen 80 Dec 1 11:56 x > > > > [repeat echo and ls -ls until...] > > > > $ echo 1234567890123456789012345678901234567890123456789012345678901234567890123456789 >> x > > $ ls -ls x > > 1 -rw-r--r-- 1 corinna vinschen 720 Dec 1 11:56 x > > $ echo 1234567890123456789012345678901234567890123456789012345678901234567890123456789 >> x > > $ ls -ls x > > 64 -rw-r--r-- 1 corinna vinschen 800 Dec 1 11:56 x2 > > ^^ > > This > For me, it goes up from 1 to 4, then in steps of 4KB. Is that a local NTFS, did you actually call chattr +S x after touching the file, and did you check with lsattr x that x is actually sparse? Corinna -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
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