Question

I have a tab-delimited text file that is very large. Some lines have the same value in the file, some lines just have unique value, For example:

a   foo
a   bar
a   foo2
b   bar2
c   bar2
c   foo3
d   bar3
...

I also have another ID list file, which is just part of the whole list. For example:

a
b
d
...

I want to get the correspond value for those ID list, the ID list is unique. How can I do it using perl script or python or basic bash command? Appreciate it!

Answer 1

In perl:

use strict;
use warnings;
use autodie;

open my $id_list, '<', 'id_list_file';
my %ids = map { chomp; $_ => 1 } readline $id_list;
close $id_list;

open my $text_file, '<', 'text_file';
while ( my $line = readline $text_file ) {
    chomp $line;
    my ($id, $value) = split /\t/, $line, 2;
    if ( $ids{ $id } ) {
        print "got value $value for id $id\n";
    }
}