How to join two files based on fields with out rearrange the colums order?

Question

I want to create a file that contains columns from two input files. File1 is like:

s,a
k,b
h,c

File2 is:

f,a
g,b 

The output should be like:

s,a,f
k,b,g
h,c,-

am using the join command like

join  -a1 -a2 -t , -1 2 -2 2 -o auto -e "-" file1 file2 > joinoutput

am getting out put like

a,s,f
b,k,g
c,h,-

please help me to fix , I cant able to specify the order of column like -o '1.1' like. if in my first file number of column is n and second file it is n i need to see n+n -1 thanks in advance

Answer 1

Replace -o auto with -o '1.1 1.2 2.1'

to get:

s,a,f
k,b,g
h,c,-

Answer 2

In perl something like this:

#!/usr/bin/env perl
use strict;
use warnings;

#Data Dumper is for diagnostic printing
use Data::Dumper;


#open second file for reading
open( my $file2, '<', 'sampleb.txt' ) or die $!;

#slurp this file into a hash (key value map) - reverse them, so we use
#the second value as a lookup key. 
my %key_values = reverse map {/(\w+),(\w+)/} <$file2>;
close($file2);

#print what we got in that map for diag reasons. 
print Dumper \%key_values;

 #open the first file
open( my $file1, '<', 'samplea.txt' ) or die $!;
#iterate by line
while (<$file1>) {
    chomp; #strip trailing line feed. 
    #split this line on comma
    my ( $key, $value ) = split /,/;
    #loopup "$value" in that hash we created - use that if it's defined, or '-' otherwise. 
    print join( ",", $key, $value, $key_values{$value} // '-' ), "\n";
}
close ( $file1 ); 

Outputs:

s,a,f
k,b,g
h,c,-