file comparison

[Dave Angel]

Hendrik van Rooyen wrote:
> On Friday 31 July 2009 11:25:17 learner learner wrote:
>   
>> Hi all,
>>
>> I want to compare two text files line by line and eliminate the
>> matching/repeated line and store the unmatched/leftout lines into a third
>> file or overwrite into one of them.
>>     
>
> This is not as simple as it seems.
>
> You will probably be better off using diff, or,
> if it is a learning exercise, studying its source.
>
> - Hendrik
>
>
>   

It is not only "not simple," it's totally underspecified.


Learner:

If this is a homework assignment, you should read the whole assignment, 
and see what it says.  Without knowing something about the text files, I 
couldn't even guess what the real goal is.

For example, if the text files are really text (e.g. a letter to 
grandma), then we want a context-sensitive comparison, the kind that 
Windiff, RCSDiff, DiffMerge, and others can do.

If the text files are each a list of items, with order and duplication 
irrelevant, then your best bet is probably to build a set from each, and 
difference the sets.

DaveA