Capturing Date/Time

[Anonymous Monk]

Hi,

I have the following string Aug 20, 2007 12:42 PM that may also optionally just be Aug 20, 2007. I'm trying to test/match/caputure both conditions in one expression. Is that possible?

This code works when the timestamp is present but obviously fails when the time is missing.

my $string = 'Aug 20, 2007 12:42 PM';
if ($string =~ /(\w{3}) (\d+), (\d{4}) (\d+):(\d{2}) (.+)/) {
   # do stuff
}

How do I make the time portion optional in that expression? This doesn't work:

if ($string =~ /(\w{3}) (\d+), (\d{4}) ((\d+):(\d{2}) (.+)?)/) {
   # do stuff
}

Thanks.

[Zaxo]

You might like Date::Parse for that. It's a lot more flexible about the datestring formats it will handle.

[FunkyMonk]

You were nearly there...

/(\w{3}) (\d+), (\d{4})(?: (\d+):(\d\d) )?/

(?: ... ) are non-capturing parentheses, so they don't muck up your dollar-digit captures.

Have you considered using split instead of a regexp? In this case it leads to much easier code to maintain

my @date_parts = split m{[\s:,]+}, $date_string;
if ( @date_parts == 6 ) {
  # date + time
} elsif ( @date_parts == 3 ) {
  # date only
} else {
  die "invalid date/time combo";
}

update: added split alternative

[logie17]

I like FunkyMonk's solution, but here's another:

if ($time =~ /^\w{3}\s\d{2}\,\s\d{4}(\s\d{2}:\d{2}\s\w{2})?/){
    print "Found it\n";
}

I'm new to regex too, but I thought I'd give a crack at it too.
Cheers!

[Nkuvu]

Don't personally like the split alternative as much. Neither approach here really do much to verify the data, but the regex is at least a bit more strict. So the regex fails to match for a string like "foo bar, baz" but the split passes it along as a valid date.

Obviously if verification of valid dates is required to prevent something like "Feb 99, 0000" for instance, then a module of some sort would probably be the best approach. (Although I can't suggest a particular module off the top of my head)

[FunkyMonk]

Validation of the data was not one of my goals, as per the OP. If it had been, I'd have used one of the (far too¹) many date modules available.

---

¹ A personal beef of mine. Don't worry about it.

[akho]

You may also like Date::Manip. It will parse a date in almost any format you throw at it.