Regular Expression from Hell

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

Replies are listed 'Best First'.
Re: Regular Expression from Hell by Abigail-II (Bishop) on Apr 15, 2004 at 15:32 UTC
You aren't anchoring, that's what's wrong with the regex. But you shouldn't use a regex in the first place. `printf "<td height=20 class=grtxt>%05d</td>\n" => $test;` [download] will do fine. Abigail	[reply] [d/l]
Re: Regular Expression from Hell by simonm (Vicar) on Apr 15, 2004 at 15:31 UTC
I think you want /\d{4}/. You can use either the + modifier or {} to indicate quantities; there's no need for both.	[reply]
Re: Regular Expression from Hell by perlmonkey (Hermit) on Apr 15, 2004 at 15:34 UTC
I think what you are looking for is: `if( $test =~ /^\d{4}$/ ) { ... }` [download] This will match: '^': anchor start of string \d{4}: exactly 4 digits $: anchor end of string if you know it is always going to be digits, then length would probably be eaiser: `if( length($test) == 4 ) { ... }` [download]	[reply] [d/l] [select]
Re: Regular Expression from Hell by eric256 (Parson) on Apr 15, 2004 at 15:35 UTC
Its hard to tell what you want since you didn't tell us specificaly. It appears however than you want to put the 0 on the front if there are only for digits? You could match for 5 and reverse your if statment or do the following. `my $test = "2123"; if($test=~/^\d{4}$/) { print "<td height=20 class=grtxt>0$test</td>\n"; } else { print "<td height=20 class=grtxt>$test</td>\n"; }` [download] I removed the + since plus means 1 or more and your {4} means four. I then added ^ to the start and $ to the end, that means the regex will only match if it matches the whoel line. So it will only be happy if the string is 4 digits exactly. I'm still not sure this is the best solution since you repeated your HTML without cause. It would be far better to modify $test or have a second variable to hold the output string. `my $test = "2523"; $test = "0" . $test if($test=~/^\d{4}$/); print "<td height=20 class=grtxt>$test</td>\n";` [download] ___________ Eric Hodges	[reply] [d/l] [select]
Re: Re: Regular Expression from Hell by Anonymous Monk on Apr 15, 2004 at 15:41 UTC
Thanks very much, it worked now!!!!!!!!!	[reply]
Re: Regular Expression from Hell by pelagic (Priest) on Apr 15, 2004 at 15:32 UTC
What's the target of that operation? Just add leading 0's with 5 digits? pelagic	[reply]
Re: Re: Regular Expression from Hell by Anonymous Monk on Apr 15, 2004 at 15:34 UTC
Is to say if a ZIP number is coming in with 4 digits only add a "0" at the begging. Else if it already has 5 digits leave it alone.	[reply]
Re: Re: Re: Regular Expression from Hell by pelagic (Priest) on Apr 15, 2004 at 15:37 UTC
`printf '%05d', $test;` pelagic	[reply] [d/l]
Re: Regular Expression from Hell by gmpassos (Priest) on Apr 15, 2004 at 20:20 UTC
Take a look at perlre, you are using wrong the syntax! `\d ## means 1 digit. \d\d ## means 2 digits. \d+ ## means 1 or more digits \d{2,} ## 2 or more \d{3} ## means 3 digits.` [download] And what you are doing just doesn't exists as you think: `\d+{4} ## means one or more digits and the text "{4}".` [download] Actually your REGEXP doesn't compile! I just don't know from where you got the idea of \d+ with {4} after it. And when you use it right you put a lot of \d before it: \d\d\d\d{4}. Note that "\d\d" already means 2 digits, and \d\d\d\d already means what you want (check if the string have only 4 digits) but you put {4} in the last, what means 7 digits! See perlre, and don't forget that perldoc.com is your friend, so, you can call it every time. Good luck. Graciliano M. P. "Creativity is the expression of the liberty".	[reply] [d/l] [select]
Re: Regular Expression from Hell by Beechbone (Friar) on Apr 16, 2004 at 21:39 UTC
What happens if the number has just 3 digits? `my $test = 123; while (length($test) < 5) { $test = '0' . $test; }` [download] or `my $test = 123; $test = ('0' x (5-length($test))) . $test;` [download] _Search, Ask, ^Know	[reply] [d/l] [select]