Question

I have an input file with two columns of integer values. I would like to chop the input file in this way

 input file:
 ...
 ...
 12312 565456
 565456 12312
 ...
 ...     

#

 output file:
 ...
 ...
 12312 565456
 ...
 ...

namely if two numbers are present in couple more then one time, writing a unique line in the output file where the first number if the smaller of the two.

How can be done with sort or a perl script?

Answer 1

You can try:

perl -nale ' @F=reverse @F if($F[0]>$F[1]);                 
             $x=$F[0]." ".$F[1]; if(!$h{$x}){print $x;$h{$x}=1;}'

See it