Sparse files in Cygwin
Lavrentiev, Anton (NIH/NLM/NCBI) [C]
lavr@ncbi.nlm.nih.gov
Wed Jul 26 17:34:00 GMT 2017
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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