how to compare two files?

[benjz]

hi! just want to ask if you have any idea in identifying difference in two files.
i have a 2 huge files(names) and i want findout if theres a duplicates... and merge it.

thank you in advance

benjz

[malleyo]

There's a program called CSDiff (free download) that you can use. It has commandline parameters that can easily be passed to it through VB code using Shell (or something similar).

[jvbd02]

Hi

If Sourcesafe is installed on the target PC (or maybe even a remote PC you can connect to, but not too sure about this one), you can use ss commands from a command prompt (shell it) or set a reference to Microsoft Sourcesafe 6.0 type library (though haven't tried this, so dunno, but I'm sure it'll work) in your vb project and identify differences and merge if any...

[benjz]

actually what i want to do is, identifying the duplicates of two files/tables. then merge it into 1 file/table. my apology if my scenario wasnt clear. hope you can give helpful tips. thank you very much!=)

[cjard]

well now, youre either talking about files, or youre talking about tables. youre going to have to be more specific

file comparison is usually done on a binary level, whereaby two files are scanned sequentially from offset zero (the start). as soon as two bytes are encountered that are different, you have a decision to make was to what to do.

most file comparators use a simple difference engine that looks for differences in absolute bytes, meaning that the following files (read as a stream left to right) are approximately 50% different:

abcdefA
abcAdef


d<>A and for every byte after, the bytes are different, e<>d, f<>e ...

other file comparators work on a line-by-line basis (source code control for example).
some smart comparators will use a gapping technique whereby, upon finding a difference, each file is searched from that point for the other byte. the one that finds first, is where comparison continues from, so our files above:


abcdefA
abcAdef

d<>A so the algorithm looks for A in the first file as well as d in the second file. It finds d after searching 1 byte, so the comparison continues from that file offset by +1byte, and the other file is not offset

so the first 3 bytes, abc in both files match
then A <> d, do when d is found in the second file +1byte, a gap of 1 byte is "inserted":

abc_defA
abcAdef


as you can see the difference enging will then find another equality of "def" in both files.. and it would come to the conclusion that the files are 80-90% identical



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comparing tables ina database is a whole other matter entirely, and you can use joins to tell you how identical two tables are.. but you need to clarify your question