Re: output unique lines only

[EdwardG]

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