It shouldn't be too hard to do, perlintro teaches you everything you need to know to accomplish it.

We are here to help you to learn perl, not to write the scripts you want. If you show some effort, we will certainly help you.

I ask, because we prefer to teach, rather than do-for, those who bow "and send Praises."

We also take the soft soap more seriously if you trouble yourself to read

• On asking for help
• How do I post a question effectively?
• Markup in the Monastery
• I know what I mean. Why don't you?

Update: upon rereading this screed, I see I've failed to be specific about the reference to "I know what I mean;..." :

Given your OP, we have no idea of the format of the "text" files in particular WRT the "first column" - are you talking about a simple text file, a CSV or Tab Delimited File or something else.

get the list of file names
declare a hash for output
open the first file
while reading each line from the file
    get the first column of the line for use as a hash key
    assign the line as the value of hash element using that key

for each remaining file
    open the file
    while reading each line from the file
        get the first column of the line for use as a hash key
        append the line to the current value of the hash element using
+ that key

for each key in the hash
     print the value of the hash element using that key
[download]

(I'm hoping I understood your task correctly -- if I didn't, please clarify.)

UPDATE: Actually, the method can be stated even more simply than what I showed above. In effect, you can leave out the part that handles the first file separately, and just do the "for" loop over all files in the list -- i.e. just treat all files in the list the same way.

You have 75% of a shell solution there. All you need to complete a shell solution is to append the grepped values onto a destination file.

On the other hand, if you want a Perl solution, go for a Perl solution. Shelling out constantly is going to be relatively expensive, so instead read the files, once. As you read each file, split it into fields and store a single row as an array. Store that array in a hash keyed by the primary field, creating the entry if it doesn't exist, appending the field values onto the existing array if it does exist.

See join - join two files according to a common key.

I get the impression that you aren't really interested in learning to program in Perl -- so go ahead and just use R, no problem there.

If you actually do want to learn perl, you might try the algorithm I proposed in my earlier reply, instead of copying code that someone else wrote and that you don't understand.

It's not hard to write a working perl script based on a decent pseudo-code description -- you just have to settle a few details, like "where does the list of file names come from?"

Here's an example that assumes the list of file names comes from command line args (which end up in @ARGV) -- that is, you would invoke the script like this:

 name_of_script  *.txt  > all-txt-files.joined
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#!/usr/bin/perl

use strict;
use warnings;

# get the list of file names -- actually, just make sure @ARGV has the
+m:
# declare a hash for output

die "Usage: $0 *.txt > text.joined\n" unless ( @ARGV and -f $ARGV[0] )
+;
my %output;

# extra step: declare an array to preserve original order of keys in f
+irst file
my @output_order;

# open the first file
# while reading each line from the file
#    get the first column of the line for use as a hash key
#    assign the line as the value of hash element using that key

open( IN, '<', $ARGV[0] ) or die "Can't read $ARGV[0]: $!\n";
while (<IN>) {
    my ( $key ) = ( /^(\S+)/ );

#  extra steps: add key to order array, turn EOL whitespace into tab c
+haracter
    push @output_order, $key;
    s/\s+$/\t/;

    $output{$key} = $_;
}

shift @ARGV;  # (extra step: removes the file name that we just handle
+d)

# for each remaining file
#    open the file
#    while reading each line from the file
#        get the first column of the line for use as a hash key
#        append the line to the current value of the hash element usin
+g that key

for my $file ( @ARGV ) {
    open( IN, '<', $file ) or die "Can't read $file: $!\n";
    while (<IN>) {
        my ( $key ) = ( /^(\S+)/ );

# extra step: turn EOL whitespace into a tab character
        s/\s+$/\t/;

        $output{$key} .= $_;
    }
}

# for each key in the hash -- using the original ordering
#     print the value of the hash element using that key

for my $key ( @output_order ) {

#  extra step: convert the final tab character into a line-feed
    s/\t$/\n/;

    print $output{$key};
}
[download]

Thanks so much for your very detailed help, very much grateful. I shall be making use of it from now onwards

Thanks again graff!