Validating Comma Delimited String

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I'd like to have a regex to evaluate whether a user has entered a valid string. Valid strings are a comma delimited set of four digit numbers i.e 9500,9501,9502

I'd like to be able to know if a user has entered anything not confirming to that pattern i.e 9500,goats,9501 or 9500,,,,,,,,, that kind of thing.

Here's what I've got so far, it kinda sorta works but doesn't capture everything. Could anyone off any suggestions?

my $string = '9500,9501';

if ($string =~ /^[\d{4}\,]+$/) {
    print "Looks ok\n";
}else {
    print "Not ok\n";
}
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Re: Validating Comma Delimited String by moritz (Cardinal) on Jan 08, 2009 at 23:31 UTC
You can't have a dynamic number of captures in Perl 5 (except perhaps with very evil hacks), so you shouldn't even try to. If you want to work with the data, split it on the comma. For validation, just use `m/^\d{4}(?:,\d{4})*$/` (assuming that one four-digit number always has to be present).	[reply] [d/l]
Re: Validating Comma Delimited String by gone2015 (Deacon) on Jan 08, 2009 at 23:37 UTC
`$string =~ /^\d{4}(?:\,\d{4})*$/` ... start, 4 digits, then any number of comma followed by 4 digits up to end (and then stop). ... and having validated, then you can `split(/,/, $string)` to "capture" the numbers.	[reply] [d/l] [select]
Re: Validating Comma Delimited String by zwon (Abbot) on Jan 08, 2009 at 23:32 UTC
`/^\d\d\d\d(,\d\d\d\d)*$/`	[reply] [d/l]
Re: Validating Comma Delimited String by Bloodnok (Vicar) on Jan 09, 2009 at 11:44 UTC
As Corion points out, you can't have a variable number of captures, but as you don't ask about/mention it explicitly, that probably isn't a problem ;-) More of a problem, however, is your use of a range (`[...]`) c/w a block/capture (`(...)`). Try ... `perl -we '$string = qq/9500,9501,fred,,9999/; map { warn qq/Bad entry: + $_ in string $string/ } grep ! /^\d{4}$/, split /,/, $string;'` [download] Gives `Bad entry: fred in string 9500,9501,fred,,9999 at -e line 1. Bad entry: in string 9500,9501,fred,,9999 at -e line 1.` [download] A user level that continues to overstate my experience :-))	[reply] [d/l] [select]