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Text file compare using PowerShell

PowerShell is able to compare text file easily.

Technet article at the link below suggest using Get-FileHash cmdlet to compare whether files are different or not.

Below code is taken from Technet link above that shows how to use the Get-FileHash method.

PS C:\> (Get-FileHash $fileA).hash  -ne (Get-FileHash $fileC).hash


PS C:\> (Get-FileHash $fileA).hash  -ne (Get-FileHash $fileB).hash


The output of the cmdlet is either True or False. True if the file is the not same with the other file, false if file is the same with the other file.

It is just true or false to check whether both files are the same or not the same.

But if files are not the same, how to check which lines or contents does not match with the other file?

In my own point of view if there is a need to check the contents, then Excel VBA will come in handy.

Link below uses VBA code to check or compare row by row.

Comparing row by row is only applicable if the files need to compare line by line and data in one line doesn't need to be compared to other data on other lines.

If the file doesn't have a consistent pattern, then it's quite difficult to compare.

Organizing the data for consistency is quite important or else it will be difficult or hard to manage once the data grows bigger and bigger.

If quite paranoid on your system and wants to monitor some particular folders what had changed over the time. Then a baseline reference is needed.

For example, during the installation of a single computer you get the baseline file for c:\Windows\System32 for all ".dll" files.

As days or months passes by you never install anything and want to check whether some new ".dll" files has been added.

You can compare the baseline text file to the current files on your system.

Of course there might be some difference since Microsoft or Windows update your system either to patch vulnerabilities or improve the system.

I think it's good to list out and compare the ".dll" files. If some unknown dll files or extra dll files during comparison comes out; which is quite suspicious then delete the file. Or backup the file before deleting.

If something goes wrong then copy over the file and check whether the system will get back to normal; but if the system goes smoothly then delete the backup “.dll” file and run system file checker to scan the system for any issues. Also run anti-virus or anti-malware software to make sure the system is not infected with any kind of virus or malware.

There are a lot of ways to do things as well as there a lot of reasons why we need to do things, so which ever method that will get the job done easily in a time efficient way should be the best choice of getting things done.

Cheers.. till next time..


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