What is the best way to produce a delta data file?

wenD has asked for the wisdom of the Perl Monks concerning the following question:

I need to begin sending data to a business partner as delta files. Previously, I've been sending them all available data on a monthly basis. But now, they would like to receive data only for the items that have changed.

My plan is to output a full file and compare that to last month's file. Lines from $current_file not found in $previous_file would be written to $delta_file.

I have some ideas on how to go about it but since my initial searches for "delta file" on CPAN and Perl Monks didn't turn up anything really obvious, I thought I would throw this out for discussion.

Comment on What is the best way to produce a delta data file?

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Re: What is the best way to produce a delta data file? by gamache (Friar) on Nov 13, 2007 at 17:55 UTC
I can't think of an easier solution than diff. It's a Unix utility, not Perl-based.	[reply]
Re: What is the best way to produce a delta data file? by Your Mother (Archbishop) on Nov 13, 2007 at 18:13 UTC
I use Algorithm::Diff for revision history in web apps. There are related modules you'll find from the POD.	[reply]
Re: What is the best way to produce a delta data file? by moritz (Cardinal) on Nov 13, 2007 at 17:57 UTC
You should really look at the unix command `diff`, it produces deltas of text files, and you can apply them with `patch`. Search for diff on CPAN will find some perl implementations or interfaces. Alternatively you could use some kind of version control system like subversion (svn) or git.	[reply] [d/l] [select]
Re: What is the best way to produce a delta data file? by KurtSchwind (Chaplain) on Nov 13, 2007 at 19:34 UTC
I see others have mentioned 'diff', which I also would agree is the way to go. There is even a windows version available via cygwin. The major caveat is that you'll want to `sort` each file before diffing. `diff` can do you wrong on unsorted files. -- I used to drive a Heisenbergmobile, but every time I looked at the speedometer, I got lost.	[reply] [d/l] [select]
Re: What is the best way to produce a delta data file? by tilly (Archbishop) on Nov 13, 2007 at 23:16 UTC
Where are you getting data from? A database? If so then you might want to look at whether you can generate an incremental data set directly. Otherwise you can use diff as others have suggested.	[reply]