Regular expression to match unique words in files

Question

To prefix unique words with "UNIQUE:" inside the file, I tried using the relx perl command, for example:

perl -e 'undef $/;while($_=<>){s/^(((?!\b\3\b).)*)\b(\w+)\b(((?!\b\3\b).)*)$/\1UNIQUE:\3\4/gs;print $_;}' demo

In a demo file containing:

watermelon banana
apple pear pineapple orange mango
strawberry cherry
kiwi pineapple lemon cranberry watermelon
orange plum cherry
kiwi banana plum
mango cranberry apple
lemon

Output:

watermelon banana
apple pear pineapple orange mango
strawberry cherry
kiwi pineapple lemon cranberry watermelon
orange plum cherry
kiwi banana plum
mango cranberry apple
UNIQUE:lemon

Unfortunately, backward link \ 3 does not seem to be processed if used in advance.

Is there any other way to achieve this with another regular expression or with other regular commands available in the Linux field ? (grep, sed, awk, ...)

Many thanks

EDIT: Unfortunately, many of the solutions only work for a case that was incomplete, my apologies for this, it should also work on the text, for example:

{watermelon || banana}
apple = ( pear pineapple orange mango )
strawberry cherry
kiwi = pineapple = lemon = cranberry = watermelon
orange - plum = cherry
kiwi = banana + plum
mango = cranberry && apple
lemon

If this simplifies the problem, words may be prefixed with something like $ or @.

Answer 1

, Perl. - , ...

#!/usr/bin/perl -w
use strict;

my %hash = ();
my $str;

while(<>) {
    $str .= $_;
    $_ =~ s/\W+/ /g;
    map {$hash{$_}++} split ' ', $_;
}

for (keys %hash){
    my $word = $_;
    if($hash{$word}==1) {
        $str =~ s/\($word)/UNIQUE:$word/g;
    }
};

print "$str\n";

:

{watermelon || banana}
apple = ( UNIQUE:pear pineapple orange mango )
UNIQUE:strawberry cherry
kiwi = pineapple = lemon = cranberry = watermelon
orange - plum = cherry
kiwi = banana + plum
mango = cranberry && apple
lemon

, , . . , , .

, $str - , , .

Answer 2

. , , , , , . , , , . ( ). , regexp, - .

s/^.*?\K(?!UNIQUE:)\b(\w+)\b(?=(?:(?!\b\1\b).)*$)/UNIQUE:\1/s

Answer 3

, ; apple cranapple, .

use strict;
use warnings;
use File::Slurp qw(read_file);

my %words;
my $content = read_file(shift @ARGV);
$words{$_} ++ for split /[\s\W]+/, $content;
my @uniq = grep { $words{$_} == 1 and length } keys %words;
$content =~ s/\b$_\b/UNIQUE:$_/g for @uniq;
print $content;

Answer 4

I don’t know why the “lemon” is unique, but let me say that I assume that this is just one occurrence of the word, and then an awk script

awk '{
 for(i=1;i<=NF;i++){
    words[$i]++
    if( words[$i] > 1){   delete words[$i]  }
 }
 a[++d]=$0
}END{
 for(i=1;i<=d;i++){
    m=split(a[i],t," ")
    for(k=1;k<=m;k++){
        if ( t[k] in words ) {
            t[k]="UNIQUE:"t[k]
        }
    }
    for(w=1;w<=d;w++){
        printf "%s ",t[w] 
    }
    print ""
 }
}' file

Exit

$ more file
watermelon banana
apple pear pineapple orange mango
strawberry cherry
kiwi pineapple lemon cranberry watermelon
orange plum cherry
kiwi banana plum
mango cranberry apple
lemon

$ ./shell.sh
watermelon banana
apple UNIQUE:pear pineapple orange mango
UNIQUE:strawberry cherry
kiwi pineapple lemon cranberry watermelon
orange plum cherry
kiwi banana plum
mango cranberry apple
lemon

Answer 5

Can you put each word on one line? If you can use the uniq command:

uniq -c yourfile

Thus, each unique word will have a score of 1.