Stumped by regex

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

Hello, Hope someone can help. I need to find a regex to take a surname (any surname) from a form with <STDIN>, It must take "double-barrel" names into account (ie those with a space in the middle), but the whole string must be no longer than 20 characters. It must start with a letter and end with a letter with the space (or no space) appearing somewhere in the middle. It must also cater for normal single word surnames. This is what i have so far (but doesnt limit to 20 characters)

m/^([a-zA-Z]\s?[a-zA-Z]?){1,20}$/
[download]

I bet this is simple but for the life of me i cant figure out the regex i need. TIA

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Re: Stumped by regex by JediWizard (Deacon) on Dec 06, 2006 at 14:55 UTC
Something like this? (It limits to strings no longer than twenty characters, nothing but letters and an optional space). `m/^(?=.{1,20}\Z)[a-z]+(?:\s[a-z]+)?$/i` [download] In the end, however, I think you'd be better off using `length` to check the string's length outside the regex. Hope this is helpful. They say that time changes things, but you actually have to change them yourself. —Andy Warhol	[reply] [d/l] [select]
Re^2: Stumped by regex by bsdz (Friar) on Dec 06, 2006 at 15:40 UTC
Except: - `'David George' =~ m/^(?=.{1,20}\Z)[a-z]+(?:\s[a-z]+)?$/i;` [download] does not return 'George'?	[reply] [d/l]
Re^3: Stumped by regex by JediWizard (Deacon) on Dec 06, 2006 at 15:58 UTC
I guess I didn't realize he needed it too... But that is only a two character change. They say that time changes things, but you actually have to change them yourself. —Andy Warhol	[reply] [d/l]
Re: Stumped by regex by reasonablekeith (Deacon) on Dec 06, 2006 at 15:05 UTC
Does it _need_ to be one regex? You might be better of checking the length first? Something like this...? UPDATE: See replies.... `if (length($name) <= 20 and $name =~ m/^\w+\s(\w+\s)?\w+$/i) { print "okay\n"; }` [download] By the way, your character restriction doesn't work because you can match up to three characters in one go within the parentheses, so your upper limit here is actually 60. --- my name's not Keith, and I'm not reasonable.	[reply] [d/l]
Re^2: Stumped by regex by brickwall (Acolyte) on Dec 06, 2006 at 15:18 UTC
Great, but wouldnt your regex also allow numbers to be entered, which i dont want Thanks	[reply]
Re^3: Stumped by regex by reasonablekeith (Deacon) on Dec 06, 2006 at 15:25 UTC
yup, dumb mistake by me. Also though, I assumed there was a first name here too. So the above regex allows an additional space that it shouldn't. You're probably okay with just the following... `$name =~ m/^[a-z]+\s?[a-z]+$/i` [download] ...although this does force a minimum length of 2. Having said this, if I'd seen JediWizard's reply, I wouldn't have posted mine. I think he nailed it first time (++). --- my name's not Keith, and I'm not reasonable.	[reply] [d/l]
Re^4: Stumped by regex by Fletch (Bishop) on Dec 06, 2006 at 15:32 UTC
Re^5: Stumped by regex by OfficeLinebacker (Chaplain) on Dec 06, 2006 at 16:19 UTC
Re: Stumped by regex by throop (Chaplain) on Dec 06, 2006 at 18:09 UTC
Others are addressing the 'how' of a regex limiting the input to 20 alpha chars. Let me ask 'Why?' Why are you refusing registration to people with non-[A-za-z] chars in their names and people with long names? What do you want to have happen when the following people try to use your form: Thomas Cartwright-Chickering (aka The Man Whose Name Wouldn't Fit) Bill Smith, Jr. Gula Agha-Venkatasubramanian Rosy O'Donnell George Talcott IV Calhoun Adams, 3rd Kurt Gödel Sriram John Jacob Jingleheimer-Schmidt Hans-Thilo Schmidt Walter de la Mare Dr. Salmon Chorsam	[reply]
Re: Stumped by regex by themage (Friar) on Dec 06, 2006 at 15:01 UTC
Hi brickwall, I think this would do what you want: `m{\A[a-zA-Z][a-zA-Z\s]{0,18}[a-zA-Z]\Z} and (@a=m{\s}g)<=1` [download] The first regexp makes sure that you have at least two chars and up to 20, including spaces. That after and make sure that you have at most a space. TheMage Talking Web	[reply] [d/l]
Re: Stumped by regex by bsdz (Friar) on Dec 06, 2006 at 15:03 UTC
I'm not sure how to do this exactly with a regex but one could use something like: - `use strict; my @names = ( 'Joe John Smith', 'David George', 'Emma Harry Sally Martin', ); foreach (@names) { my @w = split /\s/, (/\s+(\w[\w ]{0,18}\w)\s$/)[0]; shift @w while @w > 2; print "@w\n"; }` [download] Update: You can replace everything in the foreach scope with: - `(/\s+(\w[\w ]{0,18}\w)\s$/)[0] =~ /(\w+\s?\w+)$/g;` [download]	[reply] [d/l] [select]
Re: Stumped by regex by l.frankline (Hermit) on Dec 06, 2006 at 15:06 UTC
HI, If the length of the string is greater than 20 then that string is ignored and skipped to next string. `while (<DATA>) { unless (length($_) > 20 ) { if ($_=~m#^[a-zA-Z]+(\s?[a-zA-Z]+)?$#) { print $_ . "\n"; } } } __DATA__ Johnson Larry Wall GeorgeWashingtonBushBush` [download] Results: Johnson Larry Wall Don't put off till tomorrow, what you can do today.	[reply] [d/l]
Re: Stumped by regex by nevyn (Monk) on Dec 06, 2006 at 16:10 UTC
Well, you have a lot of replies, and I think they all fail your spec. ... well done :). This is probably what I would do... `sub surname { # Assumes ASCII locale $_ = shift; return undef if (length($_) > 20); return $_ if /^([a-zA-Z]+)$/; # Surname is only one return $_ if /^[a-zA-Z]+ ([a-zA-Z]+)$/; # Surname only return undef; }` [download] -- And-httpd, $2,000 security guarantee James Antill	[reply] [d/l]
Re^2: Stumped by regex by brickwall (Acolyte) on Dec 06, 2006 at 18:10 UTC
Thanx for all the replies guys. Although some of them dont quite do it. In the end i figured out that the following will do the job (with the addition of some varification error messages for the user), and then check for length with an "if". Thanx guys `m/^[a-zA-Z]+\s?[a-zA-Z]*$/` [download]	[reply] [d/l]

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