Does a Linux program exist to help me with this?
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I have a few (about 1.5 dozen) CSV files, each (well most) CSV files have a different header and different format, but they still have some shared columns.  For instance A.csv may have a "user" field as the first input field and B.csv may have a "user" field as it's 5 field, but they are the same fields encoding the same data.

I want to go through each of the columns that have shared meaning and get a list of unique strings in those columns.  so if A.csv has a user Alex and Bob and B.csv has user Alex and Eve I would want a list of Alex, Bob, and Eve.

Is there any convenient linux built-in program which will simplify this task for me?  or is it best to just write my own program from scratch for this logic?

Thanks.