[slavik81]

I started off as a PowerShell fan, but my introductory experience has been pretty poor. A little while back, I tried testing the output of a sorting algorithm with PowerShell. I wrote a line of bash to check my results:

  diff <(cat output.txt) <(cat output.txt | sort -n)

Then I wrote the PowerShell:

  get-content output.txt | foreach-object { [Int] $_ } | sort-object | out-file -encoding ascii sorted.txt
  compare-object (get-content output.txt) (get-content sorted.txt)

Yeah, it's a lot longer. It was the bug that really soured me, though. The files compare as identical even if output.txt is not sorted.

You go read Microsoft tutorials [1] and they tell you to use Get-Content (cat) and Compare-Object (diff) like this for comparing files, but what they don't tell you is that order is ignored. Given how often I see the above code cited online for comparing files [2][3], I'm not sure that many people actually understand this.

I still haven't actually figured out how you properly compare files with PowerShell. I call fc.exe now, but its output is pretty gnarly so all I use is the return value.

[1] https://technet.microsoft.com/en-us/library/Ee156812.aspx [2] http://blogs.technet.com/b/heyscriptingguy/archive/2015/04/0... [3] http://serverfault.com/questions/5598/how-do-i-diff-two-text...

[bjourne]

AFAICT, you are just trying to check if a file is sorted? Then wouldn't:

    diff (cat out.txt | sort | out-string) (cat out.txt -raw)

do it?

[slavik81]

Yeah, actually. Though, I'd still include the cast to int, because I need to sort numerically, not lexicographically.

I suppose the lesson is that if you want to preserve line order, you need to use -raw to prevent Get-Content (cat) from splitting the file into multiple lines. That still ruins the output text from Compare-Object (diff), but it's cleaner than fc.exe.

Thanks.