-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 According to James Youngman on 2/1/2005 3:17 AM: > > Unix systems automatically generate sparse files when programs seek > forwards on their output file. There is no need to have a "sparse" > attribute. This is what coreutils' "cp" does.
Right now, the tests/du/8gb test uses dd to try to create a sparse file; and strace'ing that on cygwin shows that it uses just lseek() followed by ftruncate() (no intervening write()). But the code in src/copy.c goes to great lengths to write() before calling ftruncate(), with the comment that "the kernel would truncate the file at the end of the last write operation". Which is it? Is copy doing more work than it should, or should dd also be doing a write before truncate? POSIX does say that ftruncate shall increase the size of the file in XSI systems, but allows it return an error and keep the size unchanged on non-XSI systems. I ask, because at the moment, cygwin's implementation only makes a sparse file on write() after lseek(), although the developers are considering making ftruncate() after lseek() also create a sparse file. - -- Life is short - so eat dessert first! Eric Blake [EMAIL PROTECTED] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (Cygwin) Comment: Public key at home.comcast.net/~ericblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFCAaOB84KuGfSFAYARAoXxAJ9nbKLwI8fGcdAJ9vVggGwehujbFwCgnIuv kmBzebHsRNu4iHb7q1vPGE0= =Wpzz -----END PGP SIGNATURE----- _______________________________________________ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils
