How to add columns in csv file with Perl? - csv

Question

I have a csv file contains following data. Now I want to add some extra columns at the end. In these extra columns, they have different value, but each row content is same. How can we do this with Perl?
Original csv file
Item Price Number
A 11 2
B 10 3
C 20 1
...(many lines)
...
I want to add retailer and buyer information in the end
Output csv file
Item Price Number Retailer Buyer
A 11 2 Mike Tom
B 21 1 Mike Tom
C 30 4 Mike Tom
...(many lines)
...
Each column has only 1 value, but it extends to the last row of csv file.
(The column title and value can be hardcode, it's not the point)

Answer 1

Use Text::CSV.
use strict;
use warnings;
use Text::CSV 'csv';
my $rows = csv(in => *STDIN, encoding => 'UTF-8', auto_diag => 2,
sep_char => "\t", keep_headers => \my #headers);
push #headers, 'Retailer', 'Buyer';
foreach my $row (#$rows) {
$row->{Retailer} = 'Mike';
$row->{Buyer} = 'Tom';
}
csv(in => $rows, out => *STDOUT, encoding => 'UTF-8', auto_diag => 2,
sep_char => "\t", headers => \#headers);
Assuming your CSV file is actually single-tab-separated, and getting input on STDIN and printing to STDOUT.

Answer 2

Are they CSV files? I can't see any commas in your sample data. Perhaps they are tab-separated instead.
In any case, you don't need Text::CSV for this as you're just adding data to each line.
#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
while (<>) {
chomp;
if ($. == 1) { # first line
say "$_\tRetailer\tBuyer";
} else {
say "$_\tMike\tTom";
}
}
(If you really have CSV files, then replace the "\t"s in my code with ",")
This reads from STDIN and writes to STDOUT so (assuming it's in a file called append_cols) you would call it like this:
./append_cols < your_old_file.csv > some_new_file.csv