Shell Programming and Scripting

$
$ cat test.txt
jambesh aaa india
trxxx
sdasd
mentor
asss
light
train
bbblah
$
$ perl -ne '/(.)\1\1/ && print' test.txt
jambesh aaa india
trxxx
asss
bbblah
$
$

leo@lein:~/Escritorio$ cat file.txt
sil
a
b
c
s
sil
b
a
leo@lein:~/Escritorio$ cat file.txt | sort -u
a
b
c
s
sil
leo@lein:~/Escritorio$

cat "file.txt" | sort | uniq -u

#!/usr/bin/perl
use strict;
use warnings;
if(!@ARGV)
{
	print "$0 <file>\n";
	exit(1);
}
open(FILE, q[<], "$ARGV[0]") or die("No se pudo leer el archivo $ARGV[0]\n");
my %seen = ();
while(<FILE>)
{
	$seen{$_}++;
	next if($seen{$_})>1;
	print;
}