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Full Discussion: perl/shell need help to remove duplicate lines from files
Top Forums Shell Programming and Scripting perl/shell need help to remove duplicate lines from files Post 302483206 by DGPickett on Friday 24th of December 2010 10:47:16 AM
Old 12-24-2010
OK, A. the key is not the whole line, and B. duplicates across files are bad, two complications. Reporting the duplicate means a definition of the original, expecially for non-key data.
  • If the lines have identical keys and not identical payload (fields not keys), then will file name order and order in file pick a winner?
  • We need to survey all files for duplicate keys, then extract the unique and winners to load, and the losers to report. Think of them as two important products, not picking favorites. While most days there may be no duplicates, if one day there are tons, you still want it to blast through.
  • There are two approaches to dealing with duplicate filtering. You can save every key in an associative array (magic box that recalls by value, but may not be robust in speed and stability with huge volume) or you can sort in key, priority order (more traditional and quite robust if you have the disk space. Store just the last key, process the first of every key and log the others. Worked great on tape in 1960 with 16K or RAM! :-)
  • Tagging the duplicates by original file means adding the file name to every record, possible but a bit of a luxury if not needed.
 

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LEARN ABOUT DEBIAN

tv_sort

TV_SORT(1p)						User Contributed Perl Documentation					       TV_SORT(1p)

NAME

       tv_sort - Sort XMLTV listings files by date, and add stop times.

SYNOPSIS

       tv_sort [--help] [--by-channel] [--output FILE] [FILE...]

DESCRIPTION

       Read XMLTV data and write out the same data sorted in date order.  Where stop times of programmes are missing, guess them from the start
       time of the next programme on the same channel. For the last programme of a channel, no stop time can be added.

       Tv_sort also performs some sanity checks such as making sure no two programmes on the same channel overlap.

       --output FILE write to FILE rather than standard output

       --by-channel sort first by channel id, then by date within each
		       channel.

       --duplicate-error If the input contains the same programme more than once,
			    consider this as an error. Default is to silently
			    ignore duplicate entries.

       The time sorting is by start time, then by stop time.  Without --by-channel, if start times and stop times are equal then two programmes
       are sorted by internal channel id.  With --by-channel, channel id is compared first and then times.

       You can think of tv_sort as converting XMLTV data into a canonical form, useful for diffing two files.

EXAMPLES

       At a typical Unix shell or Windows command prompt:

       tv_sort <in.xml >out.xml
       tv_sort in.xml --output out.xml

       These are different ways of saying the same thing.

AUTHOR

       Ed Avis, ed@membled.com

perl v5.14.2							    2006-03-02							       TV_SORT(1p)
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