Merging two files into one based on the first column

Question

I have two files, both in the same format -- two columns both containing a number, for example:

file 1

1.00    99
2.00    343
3.00           


        

Answer 1

A Perl-solution

perl -anE 'push @{$h{$F[0]}}, $F[1]; END{ say "$_\t$h{$_}->[0]\t$h{$_}->[1]" for sort{$a<=>$b} keys %h }' file_1 file_2 > file_3

Ok, looking at the awk-oneliner this is shorter then my first try and it has the nicer output then the awk-oneliner and it doesn't use the 'pipe sort -n':

perl -anE '$h{$F[0]}="$h{$F[0]}\t$F[1]"; END{say "$_$h{$_}" for sort {$a<=>$b} keys %h}' file_1 file_2

And the one-liners behave different then the join-example if there are entries with no value in the second column in the first file.