[ILUG] comparing files

[Brian Foster]

  | Date: Mon, 2 Feb 2004 12:55:08 +0000
  | From: "John P. Looney" <valen at tuatha.org>
  | 
  | On Mon, Feb 02, 2004 at 12:52:19PM +0000, olearypj at rte.ie mentioned:
  |  > I need to compare two VERY large files of names & extract the
  |  > lines that are not common to both.  The problem is that the
  |  > same names appear in different positions in both files.  [ ... ]
  | 
  | Have a look at the "uniq" command.  [ ... ]

 another command would comm(1).

 be aware, however, that both uniq(1) and `comm'
 require the input to be sorted.
 ( I must confess I have never understood why the
  input must be sorted.  `uniq' could still deal
  with _adjacent_ duplicate lines (e.g., N and N+1),
  and `comm' could compare line N with line N.
  why the insistence on sorting? )

 incidentally, previous posters have suggested:
       cat FILE1 FILE2 | sort | uniq --unique
 winning the “Useless Use of cat(1)‟ Award™, and:
       sort < FILE1 < FILE2 | uniq --unique
 winning the "I Didn't Test This‟ Award™.

 what's wrong with?:
       sort FILE1 FILE2 | uniq --unique
 or the `comm' (almost-)equivalent:
       sort FILE1 FILE2 | comm -3
 since sort(1) іs a _merge_-and-sort utility?

cheers!
	-blf-
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