Makeing rules in Regex for string content and size

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

Yes, I confess I'm two clowns short of a circus.

I'm trying to write a search script for a small CSV database. Its not complex enought to warrant SQL.

Basically, I want to check the incoming string from the form against the following logic:

The string must be at least 4 characters long and no more than 16
It must contain only uppercase or lowercase A-Z and/or 0-9
It can also contain {space},"&-' as punctuation characters

I want to be able to make a true/false against this to either continue the search script or warn the user to put more text into the search.

A generic regex that you can add more allowed charachters to and alter the min/max size would be good as I think this gets used a lot.

- Jed

Comment on Makeing rules in Regex for string content and size

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Re: Making rules in Regex for string content and size by Corion (Patriarch) on Jun 05, 2000 at 14:05 UTC
Such a regular expression is quite simple to make (see perlre for a long explanation). First we start with the RE for one single allowed character. To match a set or a range of characters, we must use the `[` and `]` chars : `[A-Z0-9 ,"&-']` [download] Now we want this RE to match at least four and at maximum 16 characters : `/^[A-Z0-9 ,"&-']{4,16}$/` [download] The braces tell Perl to match the previous part of the RE (our set of valid characters) at least 4 times and at maximum 16 times. There are of course other ways, for example the more clumsy way of doing it like this : `# Please excuse the long line ;) /^[A-Z0-9 ,"&-'][A-Z0-9 ,"&-'][A-Z0-9 ,"&-'][A-Z0-9 ,"&-'][A-Z0-9 ," +&-']?[A-Z0-9 ,"&-']? ... repeat total 12 times ... [A-Z0-9 ,"&-']?$/` [download] Here, the `?` tells Perl to optionally match the previous set, in fact, the `?` is equivalent to `{0,1}`. If you find yourself struggling with REs often, you might want to take a look at Mastering Regular Expressions by Jeffrey Friedel (It is published by O'Reilly, and has a big owl on the cover) - this book covers everything about REs, but I don't know how good it is for beginners. Update: Here is a direct link to the book. Update: perlcgi told me that lowercase characters should be allowed as well. D'oh ;) Here we go again : `# The set for the characters gets changed : [A-Za-z0-9 ,"&-'] # and the RE then looks like this : /^[A-Za-z0-9 ,"&-']{4,16}$/ # and we can modify the RE, so that A-Z also matches # a-z with the "i"-modifyer : /^[A-Z0-9 ,"&-']{4,16}$/i # or equivalent /^[a-z0-9 ,"&-']{4,16}$/i` [download]	[reply] [d/l] [select]
RE: Re: Making rules in Regex for string content and size by zodiac (Beadle) on Jun 06, 2000 at 17:06 UTC
You should escape the - in the character class, or it will match all characters from & to ' which is not really what you want, is it? `[A-Z0-9 ,"&\-']` [download] would be the correct form if I am right.	[reply] [d/l]
RE: RE: Re: Making rules in Regex for string content and size by nuance (Hermit) on Jun 07, 2000 at 00:43 UTC
You can just stick it anywhere that it won't be interpreted as part of a range so: `[-A-Z0-9 ,"&'] or even [A-Z-0-9 ,"&']` [download] Will work *Nuance*	[reply] [d/l]
Re: Makeing rules in Regex for string content and size by perlcgi (Hermit) on Jun 05, 2000 at 14:20 UTC
A slightly shorter version of corion's nice explanation above would be: `/^[\w ,"&-']{4,16}$/` Updated: Caveat - This will also allow underscores which is probably not what you want. Kudos to corion	[reply] [d/l]
RE: Re: Makeing rules in Regex for string content and size by gaspodethewonderdog (Monk) on Jun 06, 2000 at 17:45 UTC
then why not just do: /^A-Z0-9 ,"&-'{4,16}$/i in the first place	[reply]
RE: Re: Makeing rules in Regex for string content and size by gaspodethewonderdog (Monk) on Jun 06, 2000 at 17:46 UTC
then why not just do: /^[A-Z0-9 ,"&\-']{4,16}$/i in the first place	[reply]
Re: Makeing rules in Regex for string content and size by antihec (Sexton) on Jun 05, 2000 at 14:11 UTC
Could you show us what you tried, and why that won't work? I think pointing you to perlman:perlre is good enough for a start, else you won't learn too much :-) `-- bash$ :(){ :\|:&};:` [download]	[reply] [d/l]