I'm new in regex and I have a question.
Like in this example, https://regex101.com/r/Iak7cF/1/ how do I force
src="wow"
to be in group 1, and
title="toto"
to be in group 2?
I want to capture this kind of text in any order only if it contains:
class="formula"
Am I doing it right?
You'd better use an HTML parser
But if you really want to use regex, you have to use named groups to achieve what you want.
<img(?=[^>]*class="formula")(?=.*(?<src>src=".*"))(?=.*(?<title>title=".*")).*>
DEMO
Regular expressions are very flexible and powerful, but in general, they are not the right tool for parsing XML, HTML, or XHTML. From WinBatch:
Regular Expressions are only good for parsing text that is tightly defined. Since Regular Expressions don't really understand the context of matches, they can be fooled in a big way if the structure of the text changes. In particular, Regular Expressions have difficulty with hierarchy.
PerlMonks has a detailed explanation of why regex is not a good solution for all but the most simple of casess. They summarize it like this:
So I hope it is clear: Please, don't try to parse arbitrary XML/HTML with regexes!
Related
I am trying to replace the contents of a string which contains xml tags as follows
I want to replace the entirety of the below statement, where ABCDEF could be any random value
<originalFileName>ABCDEF</originalFileName>
How would I do this?
Solution
You can try this for your purpose:
(<originalFileName>[\w]*</originalFileName>)
Not recommended
However, note that it is not recommended.
Regular expressions are a tool that is insufficient to understand the constructs employed by XML/HTML/XHTML. XML/HTML/XHTML is not a regular language and hence cannot be parsed by regular expressions. Regex queries are not equipped to break down XML/HTML/XHTML into its meaningful parts. Even enhanced irregular regular expressions as used by Perl are not up to the task of parsing XML/HTML/XHTML.XML/HTML/XHTML is a language of sufficient complexity that it cannot be parsed by regular expressions.
Further details : RegEx match open tags except XHTML self-contained tags
This could help you:
EDITED (this new one will also accept non-characters between your tags and I have scaped the / symbol which can give some errors if not):
(<originalFileName>.*<\/originalFileName>)
Check it here.
I'm lousy at regular expressions but occasionally they're the only thing that's the right solution for a problem.
Is there something in the .NET framework that allows you to input an unencoded string and get a pattern from it? Which you could then modify as required?
e.g. I want to remove a CDATA section that contains a file from some XML but I can't work out what the right pattern is for <![CDATA[hugepileofrandombinarydataherethatalsoneedstogo]]> and I don't want to ask for help each time I'm stuck on a regex pattern.
Such tools exist, google by "regex generator".
But, as suggested in comments, better learn regex. Simple patterns are easy. Something like <!\[.*?]]>
in your case.
There are Regex Design tools like expresso...
http://www.ultrapico.com/expresso.htm
It's not perfect but as there is no suitable .Net component the text to regex page at txt2re.com is the best I've seen for those people who occasionally need to build a regex to match a string but don't have the time to relearn regex each time they want to use one.
I need to enhance the search functionality on a page listing user accounts. Rather than have multiple search boxes for each possible field, or a drop down menu where the user can only search against one field, I'd like a single search box and to use a gmail like syntax. That's the best way I can describe it, and what I mean by a gmail like search syntax is being able to type the following into the input box:
username:bbaggins type:admin "made up plc"
When the form is submitted, the search string should be split into it's separate parts, which will allow me to construct a SQL query. So for example, type:admin would form part of the WHERE clause so that it would find any record where the field type is equal to admin and the same for username. The text in quotes may be a free text search, but I'm not sure on that yet.
I'm thinking that a regular expression or two would be the best way to do this, but that's something I'm really not good at. Can anyone help to construct a regular expression which could be used for this purpose? I've searched around for some pointers but either I don't know what to search for or it's not out there as I couldn't find anything obvious. Maybe if I understood regular expressions better it would be easier :-)
Cheers,
Adam
No, you would not use regular expressions for this. Just split the string on spaces in whatever language you're using.
You don't necessarily have to use a regex. Regexes are powerful, but in many cases also slow. Regex also does not handle nested parameters very well. It would be easier for you to write a script that uses string manipulation to split the string and extract the keywords and the field names.
If you want to experiment with Regex, try the online REGex tester. Find a tutorial and play around, it's fun, and you should quickly be able to produce useful regexes that find any words before or after a : character, or any sentences between " quotation marks.
thanks for the answers...I did start doing it without regex and just wondered if a regex would be simpler. Sounds like it wouldn't though, so I'll go back to the way I was doing it and test it again.
Good old Mr Bilbo is my go to guy for any naming needs :-)
Cheers,
Adam
I am converting XML children into the element parameters and have a dirty regex script I used in Textmate. I know that dot (.) doesn't search for newlines, so this is how I got it to resolve.
Search
language="(.*)"
(.*)<education>(.*)(\n)?(.*)?(\n)?(.*)?(\n)?(.*)?</education>
(.*)<years>(.*)</years>
(.*)<grade>(.*)</grade>
Replace
grade="$13" language="$1" years="$11">
<education>$3$4$5$6$7$8$9</education>
I know there's a better way to do this. Please help me build my regex skills further.
Use an xml parser, don't use regex to parse xml.
If there are no other tags inside the <education> element, I would change that part to:
<education>([^<>]*)</education>
If possible, I would use the same technique everywhere else you're using .*. In the case of the language attribute, it would take this form:
language="([^"]*)"
I'm having a bit of trouble with my regex and was wondering if anyone could please shed some light on what to do.
Basically, I have this Regex:
\[(link='\d+') (type='\w+')](.*|)\[/link]
For example, when I pass it the string:
[link='8' type='gig']Blur[/link] are playing [link='19' type='venue']Hyde Park[/link]"
It only returns a single match from the opening [link] tag to the last [/link] tag.
I'm just wondering if anyone could please help me with what to put in my (.*|) section to only select one [link][/link] section at a time.
Thanks!
You need to make the wildcard selection ungreedy with the "?" operator. I make it:
/\[(link='\d+')\s+(type='\w+')\](.*?)\[\/link\]/
of course this all falls down for any kind of nesting, in which case the language is no longer regular and regexs aren't suitable - find a parser
Regular Expressions Info a is a fantastic site. This page gives an example of dealing with html tags. There's also an Eclipse plugin that lets you develop expressions and see the matching in realtime.
You need to make the .* in the middle of your regex non-greedy. Look up the syntax and/or flag for non-greedy mode in your flavor of regular expressions.