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Sparse files in Cygwin




Hello,

I have a question whether sparse files are supported in Cygwin.  From the source code,
it looks like they are, but from the series of the following commands, I can't confirm:

$ dd bs=1 seek=1G if=/dev/null of=sparse
0+0 records in
0+0 records out
0 bytes copied, 0.00392699 s, 0.0 kB/s

$ ls -l sparse
-rw-r--r-- 1 lavr Domain Users 1073741824 Jul 26 12:51 sparse

$ du --apparent-size sparse
1048576 sparse

$ du sparse
1048576 sparse

Same result if I create "sparse" with "touch sparse ; truncate -s 1G sparse"


Compare Linux output:

$ touch sparse ; truncate -s 1G sparse

$ ls -l sparse
-rw-r--r-- 1 lavr cppcore 1073741824 Jul 26 12:54 sparse

$ du sparse
0       sparse

$ du --apparent-size sparse
1048576 sparse


And for those who say not all UN*X is Linux, the output from FreeBSD:

> dd bs=1 seek=1G if=/dev/null of=sparse
0+0 records in
0+0 records out
0 bytes transferred in 0.000011 secs (0 bytes/sec)

> ls -l sparse
-rw-r--r--  1 coremake  cppcore  1073741824 Jul 26 12:57 sparse

> du sparse
1       sparse

> du -A sparse
1048576 sparse


Thank you,

Anton Lavrentiev
Contractor NIH/NLM/NCBI


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