Adding quotes to a CSV using perl - regex

Question

I've got a CSV that looks as follows:
A,01,ALPHA
00,D,CHARLIE
E,F,02
This is the desired file after transformation:
"A",01,"ALPHA"
00,"D","CHARLIE"
"E","F",02
As you can see, the fields that are entirely numeric are left unquoted, whilst the alpha (or alphanumeric ones) are quoted.
What would be a sensible way to go about this in Perl ?
Already commented below, but I've tried stuff like
perl -pe 's/(\w+)/"$1"/g'
And that doesn't work because \w obviously picks up the numerics.

Answer 1

I recommend not reinventing the wheel, but rather to use an already existing module, as zdim recommends. Here is your example using Text::CSV_XS
test.pl
#!/usr/bin/env perl
use warnings;
use strict;
use Text::CSV_XS;
use Scalar::Util qw( looks_like_number );
my $csv = Text::CSV_XS->new();
while (my $row = $csv->getline(*STDIN)) {
my #quoted_row = map { looks_like_number($_) ? $_ : '"'. $_ .'"' } #$row;
print join(',',#quoted_row) . "\n";
}
Output
cat input | perl test.pl
"A",01,"ALPHA"
00,"D","CHARLIE"
"E","F",02

Answer 2

Another one-liner, input file modified to add a line with alphanumeric fields
$ cat ip.csv
A,01,ALPHA
00,D,CHARLIE
E,F,02
23,AB12,53C
$ perl -F, -lane 's/.*[^0-9].*/"$&"/ foreach(#F); print join ",", #F' ip.csv
"A",01,"ALPHA"
00,"D","CHARLIE"
"E","F",02
23,"AB12","53C"
To modify OP's attempt:
$ perl -pe 's/(^|,)\K\d+(?=,|$)(*SKIP)(*F)|\w+/"$&"/g' ip.csv
"A",01,"ALPHA"
00,"D","CHARLIE"
"E","F",02
23,"AB12","53C"
(^|,)\K\d+(?=,|$)(*SKIP)(*F) this will skip the fields with digits alone and the alternate pattern \w+ will get replaced

Answer 3

It seems that you are after a one-liner. Here is a basic one
perl -lpe '$_ = join ",", map /^\d+$/ ? $_ : "\"$_\"", split ",";' input.csv
Splits each line by , and passes obtained list to map. There each element is tested for digits-only /^\d+$/ and passed untouched, or padded with " otherwise. Then map's return is joined by ,.
The -l removes newline, what is needed since " pad the whole line. The result is assigned back to $_ in order to be able to use -p so that there is no need for explicit print.
The code is very easily used in a script, if you don't insist on an one-liner.
Processing of csv files is far better done by modules, for example Text::CSV