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Re: output unique lines only

by EdwardG (Vicar)
on Dec 06, 2005 at 16:44 UTC ( #514541=note: print w/ replies, xml ) Need Help??


in reply to output unique lines only

Here's one approach -

  • Use STDIN and STDOUT for input and output
  • Use a regex to extract the first 'column'. You could also use split, but since you care only about the first column it may be overkill.
  • Use a hash to gather unique filenames

Put it all together and you will have something like this:

# uniqfiles.pl use strict; # helps prevent silly mistakes use warnings; # helpful when writing code while (<>) { # Reads from STDIN if (/^(\w+)\t/) { # If the line starts with one or more 'word' char +acters followed by a tab... my $filename = $1; # ...assume we've got a filename captured $uniq_fnames{$filename} = 1; # ...and add it to our hash. } } print $_,"\n" for keys %uniq_fnames; # prints to STDOUT, can be piped + to a file

Then you could use this as follows

perl uniqfiles.pl < my_non_unique_list_of_files > my_unique_list_of_fi +les

 


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