How to regex match a string of alnums and hyphens, but which doesn't begin or end with a hyphen?

Posted by Shahar Evron on Stack Overflow See other posts from Stack Overflow or by Shahar Evron
Published on 2010-04-23T17:11:59Z Indexed on 2010/04/23 17:13 UTC
Read the original article Hit count: 318

Filed under:

regex

|

pcre

|

assertions

|

strings

|

php

I have some code validating a string of 1 to 32 characters, which may contain only alpha-numerics and hyphens ('-') but may not begin or end with a hyphen.

I'm using PCRE regular expressions & PHP (albeit the PHP part is not really important in this case).

Right now the pseudo-code looks like this:

if (match("/^[\p{L}0-9][\p{L}0-9-]{0,31}$/u", string) 
    and
    not match("/-$/", string))

   print "success!"

That is, I'm checking first that the string is of right contents, doesn't being with a '-' and is of the right length, and then I'm running another test to see that it doesn't end with a '-'.

Any suggestions on merging this into a single PCRE regular expression?

I've tried using look-ahead / look-behind assertions but couldn't get it to work.

© Stack Overflow or respective owner

Related posts about regex

Find multiple regex in each line and skip result if one of the regex doesn't match

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a list of variables: variables = ['VariableA', 'VariableB','VariableC'] which I'm going to search for, line by line ifile = open("temp.txt",'r') d = {} match = zeros(len(variables)) for line in ifile: emptyCells=0 for i in range(len(variables)): regex = r'('+variables[i]+r')[:|=|\(](-… >>> More
OWASP Regex Repository: Is this regex correct?

as seen on Stack Overflow - Search for 'Stack Overflow'
I was looking at the regular expression for validating various data types from the (OWASP Regex Repository). One of the regular expressions in there is called safetext and looks like: ^[a-zA-Z0-9\s.\-]+$ My first question is: Is this regular expression correct? complementary question If this… >>> More
Make a Perl-style regex interpreter behave like a basic or extended regex interpreter

as seen on Stack Overflow - Search for 'Stack Overflow'
I am writing a tool to help students learn regular expressions. I will probably be writing it in Java. The idea is this: the student types in a regular expression and the tool shows which parts of a text will get matched by the regex. Simple enough. But I want to support several different regex… >>> More
JS regex isn't matching, even thought it works with a regex tester

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm writing a piece of client-side javascript code that takes a function and finds the derivative of it, however, the regex that's supposed to match with the power rule fails to work in the context of the javascript program, even though it sucessfully matches when it's used with an independent regex… >>> More
c# RegEx with "|"

as seen on Stack Overflow - Search for 'Stack Overflow'
I need to be able to check for a pattern with | in them. For example an expression like d*|*t should return true for a string like "dtest|test". I'm no regex hero so I just tried a couple of things, like: Regex Pattern = new Regex("s*\|*d"); //unable to build because of single backslash Regex Pattern… >>> More

Related posts about pcre

Convert Javascript Regular Expression to PHP (PCRE) Expression

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi all, I am up to my neck in regular expressions, and I have this regular expression that works in javascript (and flash) that I just can't get working in PHP Here it is: var number = '(?:-?\\b(?:0|[1-9][0-9]*)(?:\\.[0-9]+)?(?:[eE][+-]?[0-9]+)?\\b)'; var oneChar = '(?:[^\\0-\\x08\\x0a-\\x1f\"\\\\]' … >>> More
Can PCRE regex match a null character?

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a text source with nulls in it and I need to pull them out along with my regex pattern. Can regex even match a null character? I only realized I had them when my pattern refused to match and when I pasted it into Notepad++ it showed all the null characters. >>> More
PCRE multi line matche problem

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi guys, i have this C++ program (actually it's just a snippet) : #include <iostream> #include <pcre.h> #include <string> using namespace std; int main(){ string pattern = "<a\\s+href\\s*=\\s*\"([^\"]+)\"", html = "<html>\n" "<body>\n" … >>> More
PHP PCRE differences on testing and hosting servers

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi all, I've got the following regular expression that works fine on my testing server, but just returns an empty string on my hosted server. $text = preg_replace('~[^\\pL\d]+~u', $use, $text); Now I'm pretty sure this comes down to the hosting server version of PCRE not being compiled with Unicode… >>> More
how to match all group and subgroup in pcre

as seen on Stack Overflow - Search for 'Stack Overflow'
a ip or other string, like "11.22.33.44" or "aa.bb.cc.dd". basically, I think it is very easy, (([\d\w]+)+\.)+[\d\w]+ but the problem is which group these submatches are in. not like ip, some string is consist of lots of words+separate in pcre, I don't know how to extract it all words -- "aa bb cc… >>> More