Compare-Object gives false differences
- by Andy
I have some problem with Compare-Object. My task is to get difference
between two directory snapshots made at different times. First
snapshot is taken like this:
ls -recurse d:\dir | export-clixml dir-20100129.xml
Then, later, I get second snapshot and load both of them:
$b = (import-clixml dir-20100130.xml)
$a = (import-clixml dir-20100129.xml)
Next, I'm trying to compare with Compare-Object, like that:
diff $a $b
What I get is in some places files that were added to $b since $a, but
in some -- files that were in both snapshots, and some files, that
were added to $b, are not given in Compare-Object output. Puzzling,
but $b.count - $a.count is EXACTLY the same as (diff $a $b).count. Why
is that?
Ok, Compare-Object has -property param. I try to use that:
diff -property fullname $a $b
And I get the whole mess of differences: it shows me ALL the files.
For example, say $a contains:
A\1.txt
A\2.txt
A\3.txt
And $b contains:
X\2.mp3
X\3.mp3
X\4.mp3
A\1.txt
A\2.txt
A\3.txt
diff output is something like that:
X\2.mp3 =>
A\1.txt <=
X\3.mp3 =>
A\2.txt <=
X\4.mp3 =>
A\3.txt <=
A\1.txt =>
A\2.txt =>
A\3.txt =>
Weird. I think I don't understand something crucial about Compare-
Object usage, and manuals are scarce... Please, help me to get the
DIFFERENCE between two directory snapshots. Thanks in advance
UPDATE: I've saved data as plain strings like that:
> import-clixml dir-20100129.xml | % { $_.fullname } | out-file -enc utf8 a.txt
And results are the same. Here're excerpts of both snapshots (top 100-something lines, a.txt and b.txt), output of compare-object, and output of UNIX diff (unified). All files are UTF-8: http://dl.dropbox.com/u/2873752/compare-object-problem.zip
