On 10/11/2007, at 10:05 AM, Daniel Ouellet wrote:
Otto Moerbeek wrote:
stat -s gives the raw info in one go. Some shell script hacking
should
make it easy to detect sparse files.
Thanks Otto for the suggestion. That might help until it can be
address for good. It would help speed up some of it. (;>
This looked interesting (curiosity killed the cat?), so I started
looking at sparse files (not heard of them before.)
Is this a sparse file?
# dd if=/dev/zero of=sparsefile bs=1024 seek=10240 count=0
0+0 records in
0+0 records out
0 bytes transferred in 0.000 secs (0 bytes/sec)
# ls -lh
[--cut--]
-rw-r--r-- 1 root wheel 10.0M Nov 11 08:43 sparsefile
# du -hsc sparsefile
32.0K sparsefile
32.0K total
# du sparsefile
64 sparsefile
# stat -s sparsefile
st_dev=7 st_ino=51969 st_mode=0100644 st_nlink=1 st_uid=0 st_gid=0
st_rdev=0 st_size=10485760 st_atime=1194723829 st_mtime=1194723829
st_ctime=1194723829 st_blksize=16384 st_blocks=64 st_flags=0
So because blocks allocated = 64, and block size is (usually) 512
bytes => file is 32K (but ls and others will report 10Mb size.)
So if you scanned whatever director(y|ies) you are interested in,
If st_size > (st_blocks * 512) Then
*** this may be a sparse file?
(BUT - blocksize of 16384 is reported so I must be missing something?)
A stab at it in Perl (lifted from Perl Cookbook):
use strict;
use warnings;
use File::Find;
sub process_file {
my $f=$File::Find::name;
(my $dev,my $ino,my $mode,my $nlink,my $uid,my $gid,my
$rdev,my $size,my $atime,my $mtime,my $ctime,my $blksize,my $blocks)
=sat($f);
if ($blocks * 512 < $size) {
print "\t$f => SZ: $size BLSZ: $blksize BLKS: $blocks
\n";
print "\t" . -s $f;
print "\n";
}
}
find(\&process_file,("/home/sparse-files"));
The output is:
# perl check.pl
/home/sparse-files/sparsefile => SZ: 10485760 BLSZ: 16384
BLKS: 64
10485760
Thanks.
