Shell Programming and Scripting

#!/usr/bin/perl
use strict;
open FH,"<a.txt" or die "Can not open file";
my (@a1,@a2,$gap,$key);
while(<FH>){
	chomp;
	my @tmp=split(",",$_);
	push @a1,$tmp[0];
	push @a2,$tmp[1];
}
close FH;
for(my $i=0;$i<=$#a1;$i++){
	$gap=0;
	$key=0;
	for(my $j=0;$j<=$#a1;$j++){
		my $tmp=abs($a2[$j]-$a1[$i]);
		if ($gap==0||$tmp<=$gap){
			$gap=$tmp;
			$key=$a2[$j];
		}
	}
	print $a1[$i],",",$key,"\n";
}

# For each key in %file1,
#   1. split the key into name/start parts
#   2. search for the record in file2 that BOTH:
#     (a) the corresponding records have the same "name" field
#     (b) has the smallest difference between $start and $middleno
#         of any of the records
#   3. Print out both records in one line
#   4. Delete these record from the structures (so they cannot be matched again)
#
foreach $key (sort {$a <=> $b} keys %file1) {
  my ($name, $start) = split(":",$key);
  my $min = 2 ** 31;  # start as maximum integer
  my $smallest_key = undef;
  for (my $i=0; $i <= $#file2_middle_keys; ++$i) {
      my $current_key = $name .":". $file2_middle_keys[$i];

      # skip entries that do not match the $name in file2 (see (1a), above)
      next unless (exists $file2{ $current_key });

      # calculate difference and see  (see (1b), above)
      my $diff = abs($file2_middle_keys[$i] - $start);
      if ($i > 0 && $diff > $min) {
        # stop -- difference is getting bigger. No need to proceed.
        last;
      }
      if ($min > $diff) {
        $min = abs($file2_middle_keys[$i] - $key);
        $smallest_key = $current_key;
      }
  }
  # answer of (2b) is in $smallest_key
  if (defined $smallest_key) {
    # (3)
    print join(" ",
      @{ $file1{$key} }[1,2,3],
      @{ $file2{$smallest_key } }[3,1,2],
      @{ $file1{$key} }[0],
    )."\n";

    # (4)
    delete $file1{$key};
    delete $file2{$smallest_key };
  }
}
# - Licenced under AGPL (http://www.gnu.org/licenses/agpl.txt)
# - Author: Otheus [https://www.unix.com/members/302022384.html]

nawk '{
if(NR==FNR)
{
  arr[$1]=$2
  brr[$1]=0
}
else
{
  a=$2-arr[$1]
  b=brr[$1]-arr[$1]
  c1=(a<0)?(-1)*a:a
  c2=(b<0)?(-1)*b:b
  if( (brr[$1]==0) || (a<b))
       brr[$1]=$2
}
}
END{
  for(i in arr)
    print i" "arr[i]" "brr[i]
}' file1 file2