Capturing Date/Time

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

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
}
[download]

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
}
[download]

Thanks.

Comment on Capturing Date/Time Select or Download Code

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Re: Capturing Date/Time by Zaxo (Archbishop) on Aug 16, 2007 at 21:34 UTC
You might like Date::Parse for that. It's a lot more flexible about the datestring formats it will handle. After Compline, Zaxo	[reply]
Re: Capturing Date/Time by FunkyMonk (Bishop) on Aug 16, 2007 at 20:16 UTC
You were nearly there... `/(\w{3}) (\d+), (\d{4})(?: (\d+):(\d\d) )?/` [download] `(?: ... )` 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:,]+}, $date_string; if ( @date_parts == 6 ) { # date + time } elsif ( @date_parts == 3 ) { # date only } else { die "invalid date/time combo"; }` [download] update: added split alternative	[reply] [d/l] [select]
Re^2: Capturing Date/Time by logie17 (Friar) on Aug 16, 2007 at 21:29 UTC
I like FunkyMonk's solution, but here's another: `if ($time =~ /^\w{3}\s\d{2}\,\s\d{4}(\s\d{2}:\d{2}\s\w{2})?/){ print "Found it\n"; }` [download] I'm new to regex too, but I thought I'd give a crack at it too. Cheers! s;;5776?12321=10609$d=9409:12100$xx;;s;(\d*);push @_,$1;eg;map{print chr(sqrt($_))."\n"} @_;	[reply] [d/l]
Re^2: Capturing Date/Time by Nkuvu (Priest) on Aug 16, 2007 at 21:08 UTC
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)	[reply]
Re^3: Capturing Date/Time by FunkyMonk (Bishop) on Aug 16, 2007 at 23:35 UTC
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.	[reply] [d/l] [select]
Re: Capturing Date/Time by akho (Hermit) on Aug 17, 2007 at 08:56 UTC
You may also like Date::Manip. It will parse a date in almost any format you throw at it.	[reply]